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A study of methods of quantitative organic microanalysis

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A study of methods of quantitative organic microanalysis

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Content A Study o f Methods o f Q u a n tita tiv e Organio M ic ro a n a ly s is a 34- A T h e sis P re s e n te d to th e F a c u lty of th e D epartm ent o f C hem istry U n iv e r s ity o f S o u th ern C a lif o r n ia In P a r t i a l F u lf illm e n t 9f th e R equirem ents f o r th e Degree M aster o f A rts hy John C lark e Cosgrove May 1934 UMI Number: EP41448 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. : In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, ' a note will indicate the deletion. UMI EP41448 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. P a W ist* ® Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 4 8 1 0 6 -1 3 4 6 This thesis, w ritten under the direction of the candidate’s F aculty C om m ittee and approved by all its m em bers, has been presented to and ac- _ I __ , j i 5 Q cepted by the Council on Graduate S tu d y and ' Research in partial fulfillm ent of the require- ^ m ents for the degree of Master o f Arts ecretary D ate........ Faculty Com m ittee Chairman TABLE OF CO NTEN TS CHAPTER Page INTRODUCTION I I . HISTORICAL BACKGROUND 3 I I , MIGROBALANCE AND ITS USE 5 I I I * DETERMINATION OF CARBON AND HYDROGEN IN MINUTE AM OUNTS OF ORGANIC MATERIALS (DRY COMBUSTION OR PREGL METHOD) 9 Oxygen and P re s s u r e R e g u la tin g A pparatus 9 Combustion Tube and F i l l i n g IS A b so rp tio n A pparatus 16 A b so rp tio n o f w ater 16 A b so rp tio n o f Carbon D ioxide 18 V olum etric D e te rm in a tio n o f w ater and Carbon D ioxide 19 Course o f A n a ly sis 20 IV, DETERMINATION OF NITROGEN IN MINUTE AM OUNTS OF ORGANIC MATERIALS t MICRO-DUMAS METHOD) 24 C o rre c tio n f o r Method 24 Kipp G en erato r 26 Combustion Tube and F i l l i n g 26 Measurement o f N itro g e n 26 Course o f A n a ly sis 28 V. EXPERIMENTAL DATA 29 Carbon and Hydrogen 30 N itro g e n 32 VI. SPECIAL CONSIDERATIONS 33 V II. SUM M ARY, . WITH CONCLUSIONS 35 BIBLIOGRAPHY 37 INTRODUCTION M icrochem istry im p lie s ch e m istry on a sm a ll sc ale * Such a term h as been a p p lie d to b o th q u a n t i t a t i v e and q u a l i t a t i v e t e s t s and r e c e n tly a n o th e r term has been added; — t h a t o f "chem ical m ic ro s c o p y ," "The term chem ical m icroscopy was coined f o r th e purpose o f d i f f e r e n t i a t i n g betw een 'm ierochem ical* m ethods and t e s t s and th e a p p l ic a tio n o f th e m icroscope to th e s o l u t i o n o f chem ical problems.""*" Q u a li ta t iv e a n a l y t i c a l r e a c tio n s observed u nder th e m icroscope a re now d e s ig n a te d by t h i s term and t h a t o f "mi c ro c h e m istry " i s re s e rv e d to m o d ific a tio n s o f o rd in a ry quan t i t a t i v e a n a l y t i c a l p ro c e d u re s which d e a l w ith v ery m inute amounts o f m a t e r i a l s . The term "m illig ra m a n a ly s is " has a ls o been su g g e sted a s a means o f d e s ig n a tin g such a n a ly s is o f m inute amounts o f s u b s ta n c e s , b u t has n o t ben g e n e ra lly accepted* The q u a n t i t i e s used f o r th e e x p e rim e n ta l work o f t h i s t h e s i s were between th r e e and f i v e m illig ra m s , .Be cau se o f th e v a s t amount o f work t h a t has been done s in c e ■^•Gharaot and Mason, Chemical M icroscopy, p , 1* s m ic ro - a n a ly s is o f o rg a n ic compounds was in tro d u c e d lay F r i t z P r e g l o f th e u n iv e r s i ty o f G raz, A u s tr ia , in 1910, th e p ro b lem must o f n e c e s s ity be r e s t r i c t e d to c e r t a i n phases* 2he d e te rm in a tio n o f carbon and hydrogen by th e d ry com bustion o r F re g l method and th e d e te rm in a tio n o f n itr o g e n by th e micro-Dumas method were chosen a s t y p i c a l m ic ro -d e te rm in a ti o n s which o f f e r many o p p o r tu n itie s f o r r e s e a r c h and c o r r e l a t i o n . Ho a tte m p t was made to compare th e wet com bustion method f o r d e te rm in in g carbon and hydrogen w ith th e d ry com bustion method* ‘ i’he form er method u se s an o x id iz in g m ix tu re o f s u l f u r i c a c id and sodium d ie h ro m a te , •^E. A bderhalden, JBLandbueh d e r blochem ischen A rb e its - m ethoden* V * 1307-1356. CHAPTER I HISTORICAL BACKGROUND Q u a n tita tiv e o rg a n ic a n a ly s is was c r e a te d in 1781 By L a v o is ie r , who was th e f i r s t to d eterm in e th e co m position o f an o rg an ic su b sta n c e from th e p ro d u c ts o f combustion# He burned o rg a n ic su b sta n c e s w ith a id o f t i n d e r o r le n s in a m easured volume o f oxygen in a b e l l - ^ a r over mercury# The carbon d io x id e formed was ab so rb e d in a s o lu t io n o f a l k a l i and th e amount was c a lc u l a te d from th e volume d i f f e r e n c e . The volume o f oxygen consumed was used f o r th e com putation o f th e w a te r. The undecomposed sample was weighed and th e n e c e ss a ry c o r r e c t io n made. In 1814-1817 B e rz e liu s abso rb ed th e w a te r formed in CaClg and th e earbon d io x id e in s o l i d KOH and formed th e b e g in n in g o f th e modern method o f com bustion a n a l y s i s . L ie b ig in 1831 in tro d u c e d h i s p o ta sh bulb f o r th e a b s o rp tio n o f COg, which com pleted th e com bustion method s t i l l commonly u se d . About 1815, n G ay-Lussac, w ith Thenard, and D o b erein er used copper oxide in th e com bustion tu b e . In 1910 P r o f e s s o r F r i t z P re g l* * th e n a t th e U n iv er s i t y o f In n sb ru c h , A u s tr ia , and a f t e r 1913 a t th e U n iv e rs ity o f Graz, A u s tr ia , was fa c e d w ith th e cho ice of re p e a tin g a long and te d io u s experim ent w ith la r g e q u a n t i t i e s to o b ta in a f i s s i o n p ro d u c t o f one o f th e a c id s o f th e b i l e , o r to % , P r e g l, Q u a n tita tiv e O rganic M lo ro a n a ly s is , p , 1. 4 m odify th e q u a n t i t a t i v e a n a ly s is o f o rg a n ic s u b s ta n c e s so t h a t c o r r e c t a n a l y t i c a l f ig u r e s could be o b ta in e d w ith th e m inute amount o f p ro d u c t a lre a d y pro d u ced . He chose th e l a t t e r problem and by th e end o f 1911 had e s s e n t i a l l y so lv e d th e problem and was a b le to determ ine carbon and hydrogen in ?-13 mgm. o f o rg a n ic m a t e r i a l and n itr o g e n in 4-8 mgm, e i t h e r by measurement o f th e gas volume o r a l k a l i - m e t r i c a l l y , -B y th e ‘ C a riu s 1 method he was a b le to d eterm in e s u l f u r and h alogen in 4 -8 mgm. Of m a t e r i a l , By 1913 th e method was f irm ly e s ta b lis h e d and was b ein g i n t r o duced in to th e p r i n c i p a l u n i v e r s i t i e s o f E urope, In 1923; P r o f e s s o r P r e g l was awarded th e wobel p r iz e in c h e m istry . 4 carbon and hydrogen d e te rm in a tio n can be made in from 50-60 m in u te s; a n itr o g e n d e te r m in a tio n , micro-Dumas, can be made in from one to one and o n e - h a lf h o u rs; th e tim e f o r a m ic ro -K ^ eld ah l n itr o g e n d e te rm in a tio n i s l e s s th a n h a l f o f t h a t r e q u ir e d f o r th e m a o ro -ftjeld a h l d e te rm in a tio n . Because o f th e economy o f a l l m a t e r i a l s , o f sp a c e , and o f tim e , th e methods o f q u a n t i t a t i v e o rg a n ic m ic ro - a n a ly s is i s r a p id ly b ein g in tro d u c e d in to u n iv e r s i t y work and i s b e in g adopted to com m ercial la b o r a to r y c o n d itio n s and demands* CHAPTER I I THE MICROCHEMICAL BALANCE A N D ITS USE P r e g l recommends th e use o f a m icro ch em ical "balance c o n s tru c te d by tt«. Kuhlmann, In t h i s problem a C h r is tia n Becker m icrochem ical b a la n c e was used which was c o n s tru c te d alo n g th e same l i n e s a s th e kuhlmann b a la n c e . The m ic r o a n a ly tic a l b alan ce has a lo n g beam, 115 mm, i n le n g th and has a c o n s ta n t s e n s i t i v i t y w hether loaded or u n lo a d ed , The maximum lo a d f o r th e b a la n e e i s 25 gram s, a lth o u g h o b je c ts weighed a re u s u a lly below 20 gram s. The s e n s i t i v i t y o f th e b a la n c e i s ± 0 .0 0 1 m illig ra m s . The b alan ce i s c o n s tru c te d w ith th r e e v ery f in e k n ife edges which a re p e r f e c t l y s t r a i g h t , l i e in one p lan e and a r e p a r a l l e l to one a n o th e r. The r i d e r s c a le c o n s is ts o f 100 u n ifo rm n o tc h e s . The b alan ce i s in e q u ilib r iu m when th e r i d e r i s in th e f i r s t n o tc h on th e l e f t j a d isp lace m en t o f the r i d e r to th e one h u n d red th n o tc h c o rresp o n d s to a lo a d o f 10 mgm, in th e r i g h t pan. A d isp la c e m e n t o f th e r i d e r one n o tch on t h i s s c a le cau ses a d e f l e c t i o n o f te n d iv is io n s on th e p o in te r s c a l e . One d iv is io n o f th e p o in te r s c a le c o rre sp o n d s to 0 .0 1 m illig ra m s . With p r a c t ic e the in d iv id u a l swings o f th e p o i n t e r can be r e a d to the o n e - te n th o f a d iv is io n and th e ac cu racy o f 0 ,0 0 1 m illig ra m s can be o b ta in e d . Two c o n s e c u tiv e re a d in g s a re s u b tr a c te d one from a n o th e r i f they are on o p p o site s id e s o f th e zero p o in t and a re added i f th e y a re b o th to th e l e f t o r to th e r i g h t o f th e s c a l e . I f th e mean d e f l e c t i o n i s to th e l e f t t h i s w eight m ust be s u b tr a c te d from th e sum o f th e w e ig h ts on th e r i g h t hand pan and th e w eig h t c o rre sp o n d in g to th e r i d e r re a d in g , i f th e mean d e f l e c t i o n i s to th e r i g h t th e w eight i s added to t h a t o f the r i g h t hand pan and the r i d e r re a d in g . 'ihe n e c e s s a ry c a l c u l a t i o n s can be made w ith ease as th e swings a re slow and the r e d u c tio n s in th e swing due to f a tig u e a re m inute and r e g u la r . An easy check on th e s e n s i t i v i t y o f th e b a la n c e w ith or w ith o u t a lo ad can be made by moving th e r i d e r one n o tch to the r i g h t . The sum o f t h i s d e f l e c t i o n and t h a t of th e p re v io u s d e f le c tio n b e fo re changing the p o s i t i o n o f th e r i d e r sh o u ld be 0 .1 m illig ra m s . In o rd er to p re v e n t j a r r i n g and undue in flu e n c e from te m p e ra tu re and l i g h t , th e b a lan ce case i s p la c e d on a mar b le s la b which h as been p la c e d on f o u r ru b b e r s to p p e rs in a g la s s c a s e , l i g h t i s p ro v id ed by a h igh c e i l i n g lamp* Ih e b alance ea se door i s l e f t open b efo re any w eigh in g i s done to in su re com plete e lim in a tio n o f any p o s s i b i l i t y o f d iff e r e n c e s o f tem perature and m oistu re in th e room and w ith in th e c a s e . The h eat from the hand as the w eig h ts or lo a d s are p la ced on the pans i s s u f f i c i e n t to cause an e r r o r in w eig h in g , to o f f s e t to a c e r ta in e x te n t such an erro r the oth er hand i s a ls o p la ced in th e b alan ce near the o th er pan to a ssu re ap proxim ately even h e a tin g . 7 As a s u b s t i t u t e f o r th e th i n w alled f l a s k w ith le a d s h o t t h a t i s recommended by r r e g l as a c o u n te rp o is e , a g la s s rod o f a p p ro x im a te ly the same w eig h t and th e same s u rfa c e a re a i s suspended from th e r i g h t hand pan* T his rod i s su b m itte d to th e same tre a tm e n t a s th e a b s o r p tio n tu b e s and is suspended n e a r th e a p p a ra tu s d u rin g com bustion. B efore w eighing b o th the c o u n te rp o is e and the a b so rp t i o n tu b e s a re rubbed v ig o ro u s ly w ith a p ie c e o f m o isten ed f l a n n e l , th en wiped w ith d ry f la n n e l fo r a m in u te. ®hey a re hung above th e b a la n c e pans and a f t e r fo u r m in u tes a re w eighed. They a re th e n a g a in wiped and a f t e r a fo u r m inute p e rio d a re weighed again* The two w eighings should check. * IS 5 .. ■ ^ ‘ .fc «* 3t I S B £ * § 'V. f i S ' O'*: 1 Im £ SB & C f \ : \ N "> < i s H K © I I & & § i i j © u: lu & 'J I -5^ § § : > » ii i? > /i i? * f p $ fcjp.S 5 - U j _ - 4 » . k (^ C i 4 i ^ < n U j * » . © 3t ^ § F - s < * ° w v. > ° P * w y „ - Ji i'- & 5 5 S » s a &* ! ! ~ ! ^ i> s & 3 i % ^ 5 ^ C * a «J lb K • £ ; £ « 1 451 5 !i{I ^ S * * * c K 18.2 I I I V J' S J . ? m i r 1 j i «? * 4 ^ © K / I CH APTER I I I DETERMINATION OP CARBON AND HYDROGEN IN MINUTE AM OUNTS OP ORGANIC MATERIALS (DRY COMBUSTION uR PREGL METHOD). OXYGEN A N D PRESSURE REGULATING APPARATUS Commercial oxygen produced by the f r a c t i o n a t i o n o f liq u id a ir i s p r e fe r a b le to th a t produced from p otassiu m c h lo r a te and manganese d io x id e , alth ou gh th e form er may carry m inute amounts o f organ ic m a tter. E rrors due to such im p u r itie s or to vap ors g iv e n o f f by new rubber tu b in g can be co r re c te d through th e u se o f a sh o rt p reh ea ter c o n ta in in g copper oxid e h ea ted to r e d n e ss. The p reh ea ter i s fo llo w e d by a u -tu b e c o n ta in in g s u it a b le a b so r p tio n m a te r ia ls . The rubber co n n ectio n s can be a r t i f i c i a l l y aged in a d ryin g oven by a s p ir a tin g a ir at 100 d eg rees to 110 d eg rees cen tig ra d e through i t w ith a water-pum p.^ Rubber tu b in g o f about 8 mm. o u ter d iam eter and 2 m m . bore i s p la ced in a f la s k co n ta in in g m olten v a s e lin e , and th e f la s k 2 evacuated on a b o ilin g w ater b a th . A ir i s re -a d m itted in o rd er to fo r c e th e v a s e lin e in to i n t e r s t i c e s in th e tu b in g . le n g th s o f 15 mm. and 20 mm. are u sed , xhe tu b in g i s d rained and f i r s t wiped in s id e w ith 'a sm all wad o f c o tto n im pregnated w ith g ly c e r in e , fo llo w e d by a dry wad o f c o tto n . The rubber co n n ectio n s can a ls o be prepared by b o ilin g the tu b in g w ith 1 P. P r e g l, Q u a n tita tiv e urganio M io r o a n a ly sis, p . 1 8 , P r e g l, op. c i t . , p . 4 4 . 10 40-5Q;& c a u s tic a l k a l i s o lu t io n , w ashing th o ro u g h ly and th e n p a s sin g h o t a i r th rough th e tu b in g .1 A ir which i s u sed in the a n a ly s is m ust a ls o be f r e e d o f a l l vap o rs o f o rg a n ic s o lv e n ts which may be p r e s e n t, The p r e h e a te r w i l l a ls o remove th e s e . D uring th e co u rse of th e a n a ly s is th e v e l o c it y o f the oxygen and o th e r g a se s p a s s in g th ro u g h th e tu b e must be con s t a n t i n o rd e r to produce th e b e s t r e s u l t s , xhe v e l o c it y i s g r e a t l y dependent upon th e p re s s u re a t which the oxygen i s in tro d u c e d and th e ‘drag* which can be e x e r te d a t the e x i t o f th e com bustion tu b e , xo a s s u re alm o st c o n s ta n t v e l o c it y a p re s s u re r e g u l a t o r and a s p i r a t o r a re employed a s shown in th e draw ing (F ig . 1 ) . xhe p re s s u re r e g u l a t o r c o n s is ts o f a b e l l g a s -h o ld e r w ith a lo n g tube th ro u g h which th e a i r i s in tro d u c e d and a s id e arm e x i t tu b e , The h o ld e r i s immersed in a b o t t l e o f w a te r c o n ta in in g a l i t t l e c a u s tic soda and i s h e ld i n p la o e w ith a p e r f o r a te d ru b b e r s to p p e r. The p re s s u r e head (F ig . 1) i s p r o p o r tio n a l to the d if f e r e n c e between the w a te r l e v e l o f th e in n e r tube and t h a t o f th e o u te r b o t t l e and sh o u ld be eq u a l to t h a t o f th e s u c tio n head Eg o f th e a s p i r a t o r . The h a l f l i t e r a s p i r a t o r b o t t l e i s f i t t e d w ith a two h o le d ru b b e r s to p p e r th ro u g h which a tu b e i s in tro d u c e d and co n n ected by ru b b e r tu b in g to th e com bustion a p p a ra tu s . A g la s s tube i s a tta c h e d to th e s id e arm o f the "^A. F r i e d r i c h , C o n t r i b u t i o n s to th e Technique of the Q u a n tita tiv e M ic r o - a n a ly tic a l D e te rm in a tio n o f Carbon and H ydrogen," Chem. Abs. XVII (1924), 29. 11 a s p i r a t o r P o t t l e , As th e w ater d r ip s from t h i s tube I t p ro duces s u f f i c i e n t s u c tio n to keep the g a se s flow ing c o n tin u o u s ly th ro u g h th e com bustion and a b s o rp tio n tuibes. The two p re s s u r e .r e g u la to r s , one f o r a i r th e o th e r f o r oxygen a re c o n n e cte d by a th re e -w a y cook to th e p r e h e a te r , o r d i r e c t l y to th e bubble c o u n te r i f th e p r e h e a te r i s not u se d , The bubble c o u n te r c o n ta in s a few drops of concen t r a t e d s u lfu ric r a c id or 50$ p o ta ssiu m h y d roxide s o l u t i o n . T h is c o u n te r (F ig , 2) i s c o n n e cte d to a U -tube one arm o f w hich i s f i l l e d w ith soda lim e h e ld in p la c e w ith g la s s wool and th e o th e r a m f i l l e d w ith g ra n u la te d ca lciu m c h l o r id e . Those m a te r ia l s t h a t are used in th e a b s o rp tio n tu b e s must a ls o be used in th e d ry in g t r a i n and where p o s s ib le th e y sh o u ld be from th e same l o t . The ta p e re d end of th e U^tube i s in s e r t e d in to th e ru b b e r s to p p e r of the com bustion tu b e . The com plete a p p a ra tu s is t e s t e d f o r le a k s and c a l i b r a te d , t h a t i s , the g as volume which p a s s e s th ro u g h th e tu b e in one m inute must be c o r r e l a t e d w ith the fre q u en cy o f th e b u b b le s in th e c o u n te r. The volume o f oxygen p e r m inute r e q u ir e d fo r th e com bustion i s between th re e and f o u r cu b ic c e n tim e te rs . 12 COMBUSTION TUBE AND FIBBING The com bustion tu b e c o n s is ts o f a t h i c k w a lle d P yrex g la s s tube 40 c e n tim e te rs in le n g th w ith an o u te r d ia m e te r o f 11 m illim e te r s , A s m a lle r tube i s s e a le d t o one end. Very s a t i s f a c t o r y r e s u l t s have been o b ta in e d u s in g Copper tu b e s w ith s l i g h t l y d i f f e r e n t f i l l i n g , 1 The " u n iv e r s a l f i l l i n g " as recommended by P r e g l can be u sed to an aly ze a c c u ra te ly any su b stan ce w h eth e r i t con t a i n s h alo g e n , s u l f u r o r n itr o g e n . The ex p erim en ts o f P r e g l have proved t h a t le a d p e ro x id e i s a r e l i a b l e ab so rb in g ag e n t f o r h ig h e r o x id e s o f n itr o g e n . Because of th e ten d en cy of t h i s re a g e n t to a ls o r e t a i n m o is tu re th e te m p e ra tu re is k e p t c o n s ta n t by means o f a h e a tin g m o rta r ( I o f Fig* 1 ) , a s the m o istu re c o n te n t rem ains c o n s ta n t w ith the te m p e ra tu re . Bead chrom ate and m e t a l l i c s i l v e r are g e n e r a lly used to r e t a i n th e h alo g en s and s u lfu r* The a c tu a l o x id iz in g f i l l i n g 2 o f th e tu b e is w ire-fo rm copper o x id e . 2 B inder has recommended th a t the le a d p e ro x id e be 4 r e p la c e d by red u ced copper and Wise ad v o c a te s t h a t th e s i l v e r w ire o r wool be re p la c e d by p l a t i n i z e d a s b e s to s . In c r e a s in g th e amount of le a d chrom ate w i l l p e rm it the com b u s tio n o f s u b sta n c e s h ig h in s u l f u r . A* Avery, J , B rachenbury, and W . M aclay, "The M etal Tube in M icro- and Sem i-m icrooom bustion A n a ly s is .? I n d . Eng* Chem. , A n al. E d ., IV (1 9 3 2 ), 238-9. P r e g l, Q u a n tita tiv e O rganic M ic ro a n a ly s is , p . 24. ^J* B in d er, "Sources o f E r r o r in O rganic E lem entary A n a ly s is ." Bar* 65B (1932), 1696-1706, 4B* W ise, "A S im p lifie d M icro-C om bustion," J , Am. Chem. Soc. XXXIX (1917), 2065-68. F t<s>. 2 . U - r r n w ith b u b b le c o w r e * F / & . 3 . f / L L e o c o M a u s r t o N r i m 14 Pumice and cesium oxid e are a ls o recommended by Clark'*' 2 and L in d e n f ie ld as c a ta l y s ts * The a d d itio n o f sm a ll q u a n ti- t i e s o f ir o n o r n ic k e l oxide and o f p o tassiu m d ich ro m ate and le a d ehromabe r e s u l t s in the s a t i s f a c t o r y com bustion o f sim p le o rg a n ic and in o rg a n ic c y a n id e s , complex c y a n id e s , f e r r o - c y a n id e s , etc* The com bustion tu b e i s c le a n e d w ith s u lfu ric -c h r o m ic a c id m ix tu re and i s r e p e a te d ly washed w ith w a te r, r in s e d w ith a lc o h o l and d r ie d w ith a i r w h ile warming. The f i l l i n g f o r the com bustion tube (F ig . 3) c o n s is ts o f: 1. A wad of s i l v e r wool o r tu r n in g s 10 mm. long# 2. Layer o f f r e s h l y ig n i t e d Gooch c r u c ib le a s b e s to s . 3 . 20-25 mm. le n g th o f le a d p ero x id e a s b e s to s p re p a re d a c c o rd in g to P r e g l. (JSxcess d u s t removed w ith c o t t o n . ) 4* Three 2 mm. l a y e r s o f a s b e s to s t i g h t l y packed (p ro v id e s th e g r e a t e s t gaseous f r i c t i o n o f whole sy ste m ). 5 . Loosely packed la y e r of s i l v e r wool 30 mm. lo n g . 6. T hin la y e r o f a s b e s to s . 7. L ayer o f a m ix tu re of copper oxide and le a d chrom ate made by s p r in k lin g f r e s h l y p r e c i p i t a t e d and d r ie d le a d chrom ate o v er copper oxide h e a te d to re d h e a t 140 mm. 8* Thin la y e r o f a s b e s to s . 9# L ayer of s i l v e r wool 25-30 mm. in le n g th . The com bustion tube is h e a te d by a s in g le u n i t e l e c t r i c fu rn a c e which i s c o n t r o ll e d by a r h e o s t a t . A te m p e ra tu re •4s. C lark, "Semi-Micro D e te rm in a tio n o f Carbon and H ydrogen." J . A ssoc. O f f i c i a l A gr. Chem. XVI (1933), 4 1 3 -8 . SK. L i n d e r f i e l d , "The M ic ro a n a ly tic a l D e te rm in a tio n o f Carbon and H ydrogen." Chem. Abs. XXIV (1930), 2402. 15 o f 1100 d e g re e s C e n tig rad e can be o b ta in e d . T his fu rn a c e i s fo llo w ed im m ediately by a hollow m o rta r f i t t e d w ith a r e f l u x co n d e n ser. T h is i s h e a te d w ith a Bunsen b u rn e r and c o n ta in s a f r a c t i o n o f a " n e a r - t u r p e n t i n e w i t h a b o ili n g p o in t o f 174-181 C. The hollow m o rta r i s used to keep the le a d p e r oxide a t a c o n s ta n t te m p e ra tu re . A p e r f e c t l y f i l l e d and ig n it e d com bustion tu b e , i f c a r e f u l l y t r e a t e d , can , a c c o rd in g to P r e g l, be used fo r 200 to 300 a n a ly s e s . The f i r s t la y e r o f s i l v e r wool m ight have to be re p la c e d i f c o n s e c u tiv e s e r i e s o f com bustions o f sub s ta n c e s c o n ta in in g h alo g en and s u l f u r c o n ta m in a te s i t . ■kpregl recommends th e u se of te c h n i c a l oymene in th e hollow m o rta r th ro u g h which means a c o n s ta n t te m p e ra tu re o f 176°G. can be m a in ta in e d . " N e a r-tu rp e n tin e " i s a p etro le u m f r a c t i o n which can be f r a c t i o n a l l y d i s t i l l e d and a p o r tio n having a c o n s ta n t b o ili n g p o in t betw een 174° and 176f G. can be e a s i l y o b ta in e d . 16 ABSORPTION APPARATUS S tr a i g h t tube a b s o rp tio n v e s s e ls (P ig . 4) f i t t e d w ith g ro u n d -g la s s s to p p e rs a r e used f o r th e a b s o rp tio n o f carbon d io x id e and m o is tu re . Two c a p i l l a r y c o n s t r i c t i o n s w ith an ante-cham ber betw een them in f r o n t of th e a b s o rb in g ag e n ts e n s u re s a h ig h degree o f co n stan c y of w eig h t. T his is due to a r e s u l t i n g v a r ia b le d i f f u s i o n p o t e n t i a l which o c c u rs when th e d i f f u s i n g m o istu re re a c h e s th e w ider p o r tio n between two c a p i l l a r i e s . The g ro u n d -g la ss j o i n t i s s e a le d w ith K ronig g la s s cem ent. The e x c e ss i s removed m e c h a n ic a lly and th e j o i n t c lean e d w ith a l i t t l e benzene. The g ro u n d -g la s s j o i n t o f the w a te r a b s o rp tio n tu b e must n o t a d jo in th e warmed neck o f th e com bustion tu b e . A b so rp tio n o f w ater V ario u s ab so rb in g a g e n ts f o r m o istu re have been used w ith v a ry in g d e g re e s o f su c c e ss by ex p e rim e n to rs in th e f i e l d . PregX*" recommends calcium c h lo r id e o f g r o a t s i z e . T hat which i s g e n e r a lly used i s th e anhydrous 20 mesh foamu A ll anhydrous GaClg, u n le s s s p e c i a l l y t r e a t e d , c o n ta in s a p p re c ia b le q u a n t i t i e s o f lim e . Lime i s a m arkedly l e s s e f f i c i e n t d ry in g ag en t th a n i s GaClg , and i f a p p re c ia b le amounts o f lim e a re p r e s e n t in th e GaClg of the a b s o rp tio n t r a i n , h ig h r e s u l t s m ight be e x p e c te d . The CaClg used fo r th e d e te rm in a tio n o f HgO may be f r e e d from lim e by tre a tm e n t 2 w ith carbon d io x id e . ^P. P r e g l, Q u a n tita tiv e O rganic M io ro a n a ly s is ♦ p . 38, W ise, nA S im p lifie d M icro-'dom bustion.” J . "Am. Shem. Soo. XXXIX (1 9 1 7 ), 2055-68. 17 The w a te r a b s o rp tio n tube i s packed w ith CaGlg between l a y e r s o f g la s s wool. When n o t i n use th e ca lciu m c h lo rid e tu b e and the carbon d io x id e a b s o rp tio n tube sh o u ld be k e p t s e c u r e ly "capped” w ith a s h o r t le n g th o f o n e -e ig h th in c h ru b b e r tu b in g plugged w ith a s h o r t p ie c e o f 4 mm. g la s s ro d , th e g la s s s u rfa c e o f th e rod m eetin g th a t of th e a b s o r p tio n tube* A calcium c h lo rid e tu b e , p ro p e rly f i l l e d , may be used fo r 10-15 com bustions w ith o u t re c h a rg in g . Anhydrone has been recommended by K irk and M cC alla,'1 ' a s a s u i t a b l e s u b s t i t u t e f o r anhydrous calciu m c h lo r id e . Over 100 a n a ly s e s can be made w ith one f i l l i n g o f th e a b so rp t i o n tu b e s , w ith o u t a l o s s in a c c u ra c y . Brew and P o r te r su g g e st t h a t phosphorous p e n to x id e can be used f o r th e a b s o rp tio n o f m o is tu re , i t 1 i s mixed in a sto p p e re d b o t t l e w ith g la s s w ool, c u t in to s h o r t p ie c e s w ith s c i s s o r , and i s k e p t in p la c e in th e a b s o rp tio n tu b e by com p r e s s e d wads of c le a n g la s s wool a t e i t h e r end, The a b s o rp tio n of m o istu re of PgOg i s so lo c a l i z e d t h a t i n d i c a t i o n o f th e moment f o r r e f i l l i n g i s o b se rv a b le by e y e . The g a in in w eight o f each a b so rb in g tu b e , d u rin g th e n e c e s s a ry p e rio d in the b a la n c e room b e fo re the w eight i s o b serv ed i s v e ry l i t t l e g r e a t e r w ith bhan i t i s w ith GaCl as a f i l l i n g . In humid w eath er °he g a in s a re 0 .0 1 5 mgm? per q u a r te r hour fo r each P©0g (0.010 mgm. f o r each CaClg tube} in d ry w eath er each PgOg tu b e g a in s o nly 0.005 mgm. o r even l e s s , i t i s s u f f i c i e n t to d eterm in e each day th e "w a itin g e r r o r ” o f th e tu b e , by o b se rv in g the i n c re a s e o f w eig h t a t th e end o f one hour; the tu b e s alw ays b ein g c le a n e d in th e u s u a l manner a q u a r te r o f an hour b e fo re b ein g w eig h ed .2 *P. K irk and A. M cCalla, "A Convenient M icro-Com bustion Method f o r Carbon and Hydrogen -D e term in a tio n ,” Chem. Abs. XXVI (1932), 5868. H, Brew and C. P o r t e r , "P re g l* s M ie ro a n a ly tic a l Method f o r the B e te rm in a tio n o f Carbon and H ydrogen,1 1 J . Soc. Chem. In d . XLVII (1928}, 17-211. 18 Alumina p re p a re d , a c c o rd in g to F is c h e r ,^ w ith 12-mesh pumice and bO'ft AlClg.6HgO s o lu t io n h e a te d i n an e l e c t r i c m u ffle u n t i l no more hCI i s evolved a t 700-750 C, forms a m ix tu re of pumice and AlgQg which i s cap ab le of ab so rb in g c o n s id e ra b le amounts of w a te r. A b so rp tio n o f Carbon D ioxide An a b s o rp tio n tube o f th e same c o n s tr u c tio n as th a t u sed f o r m o istu re i s f i l l e d f o r th e a b s o rp tio n o f carbon 2 s io x id e . P r e g l ad v o c ate s m o ist so d a -lim e a s a s u i t a b l e ab so rb in g r e a g e n t. F ollow ing a sm a ll p le d g e t o f g la s s wool, 8 ,5 cm. la y e r of m o ist so d a-lim e ( c o n ta in in g 10-13^ of Hg0) i s in tro d u ced in to th e tu b e . T his i s fo llo w e d by a 1 cm. la y e r o f d ry so d a -lim e and a wad of g la s s w ool. A 1 ,5 cm. l a y e r of calcium c h lo rid e and a n o th e r sm a ll wad o f g la s s wool com p letes th e f i l l i n g fo r th e tu b e . T h is tube sh o u ld be c le a n e d and re c h a rg e d a f t e r each com bustion. The carbon d io x id e a b s o rp tio n tu b e a s u sed by Drew 3 and P o r t e r i s f i l l e d w ith th e m ix tu re of Pg05 and g l a s s wool to l e s s th a n h a l f i t s le n g th and th en to th e s to p p e r w ith d ry so d a -lim e , a com pressed wad o f g l a s s wool b ein g p ro v id ed betw een th e so d a-lim e and th e p e n to x id e , and a t each end o f th e tu b e , A ccording to Drew and P o r t e r , "The p r e v a ilin g o p in io n t h a t so d a -lim e s ab so rb s carbon d io x id e only when ■Hi. F is c h e r , F. F a u s t, and G. Walden, "Alumina as an A bsorbent f o r W ater in O rganic Com bustion", J . In d . Eng. Chem. XIV (1 9 2 2 )., 1138-9. ^F. P r e g l, Q u a n tita tiv e O rganic M icroscopy, p . 38. Drew and C. S o r t e r , " P r e g l' s M ic ro a n a ly tic a l Method f o r th e D e te rm in a tio n o f Carbon and h y d ro g e n ," J , Soc, Chem. In d . XLVII, (1928), 17-21T. 19 m o ist can h a r d l y be c o r r e c t . " '^he use o f g r e a t l y p ro lo n g s th e a c tiv e l i f e o f th e so d a -lim e in th e CQ2 a b so rb in g tu b e . A s e a r ite ^ has been used f o r th e a b s o r p tio n o f carb o n d io x id e and r e s u l t s o b ta in e d by th e u se o f t h i s re a g e n t have been s a t i s f a c t o r y . The a b s o rp tio n tu b e s must be clean ed th o ro u g h ly b e fo re w eighing by w iping them c a r e f u l ly w ith a p ie c e of m o ist f la n n e l and th e n w ith d ry f l a n n e l , The s u r fa c e of th e tube i s rubbed f o r one m inute and th e n th e tube i s p la c e d on a c o u n te r-p o is e d tube h o ld e r on b a la n c e pan, and weighed a t th e end o f f o u r m in u te s. The tu b e i s th e n removed from th e b a la n e e pan a g a in wiped f o r one m inute, and weighed a t th e end o f fo u r m in u tes. I f th e d if f e r e n c e between th e two w eighings i s g r e a t e r th a n 0 .0 5 mgm., th e e n t i r e o p e r a tio n i s r e p e a te d , The tu b e s a re removed and p la c e d on th e b a la n c e by means o f alum inium f o r k s . V olum etric d e te r m in a tio n o f W ater and Carbon d io x id e 2 L in d er ■ has had s u r p r i s i n g l y a c c u ra te r e s u l t s d e t e r m ining th e amount o f w ater and carbon d io x id e r e s u l t i n g from a com bustion v o lu m e tric a lly * W ith cane su g a r c o n ta in in g 6 ,4 8 $ hydrogen, 4 2 .0 9 $ ca rb o n , th e v a lu e s o b ta in e d w ith 22.5 mgm. o f su b sta n c e were 6 .4 2 $ and 4 2 .0 6 $ . ^he carbon d io x id e and w a te r from th e com bustion tube a re p a sse d in to c h lo ro - ■^E. C la r, "Semi-M icro D e te rm in a tio n o f Carbon and H ydrogen," J . A ssoc. O f f i c i a l A gr. Chem. XVI (1933), 4 1 3 -1 8 . L in d e r, ^V olum etric De terrain a t ion of Carbon and Hydrogen in O rganic Compounds," Chem. Abs, XVI (1 9 2 2 ), 3605. £0 n ap h th y lo x y o h lo ro p h o sp h in e CioHgCiaPQClg. compounds h y d ro ly z e s and two m o le cu les of HGl a r e l i b e r a t e d f o r each m o lecu le o f w a te r. The r e s u l t i n g m ix tu re o f carbon d io x id e and w a te r can be a n a ly z e d v o lu m e tr ic a lly . A f t e r a b s o rp tio n in a m easured volume o f O .In Ba(GH)g, t i t r a t i o n w ith a c id in th e c o ld w ith p h e n o lp h th e in a s an i n d i c a t o r g iv e s th e e x c ess Qf a l k a l i and t h i s s u b tr a c te d from th e o r i g i n a l volume g iv e s th e volume o f Ba(0H)g which h as r e a c te d w ith HGl and GOg. Then i f th e s o lu t io n i s t i t r a t e d h o t w ith th e same i n d i c a t o r , th e t o t a l volume o f a c id now co rre sp o n d s to th e e x c e s s of Ba{0H)g and to th e BaOQg form ed; by s u b tr a c tin g t h i s from th e t o t a l volume of a l k a l i , th e volume e q u iv a le n t t o th e HC1 i s o b ta in e d . Course o f th e A n a ly s is The com bustion tu b e i s p re h e a te d in a c u r r e n t o f a i r and th e hollow m o rta r i s h e a te d u n t i l th e l i q u i d b o i l s . The a i r i s re p la c e d by a c u r re n t o f oxygen and th e p r e s s u r e reg*^ u l a t o r i s a d ju s te d to m a in ta in th e n e c e s s a ry g as v e l o c it y o f 3-4 cu b ic c e n tim e te rs p e r m in u te . The weighed a b s o rp tio n tu b e s a re in te rc o n n e c te d a t th e b alan ce w ith th e t r e a t e d ru b b e r c o n n e c tio n s , and a r e hung from w ire s u p p o rts n e x t to com bustion tu b e . The ca lciu m e h lo rid e tu b e i s a tta c h e d to th e neck o f th e com bustion tu b e and the so d a -lim e tube i s th e n co n n ected to th e a s p i r a t o r th rough th e ca lciu m c h lo rid e tu b e . The g la s s p o r tio n s o f th e c o n n e c tio n s sh o u ld be in imm ediate c o n ta c t. 21 The ru b b e r s to p p e r i s th en removed from th e com bustion tube and th e b o a t, h e ld w ith fo ro e p s , i s pushed in to th e open tube* I t i s pushed forw ard w ith a c le a n g l a s s ro d u n t i l i t i s about 15 mm. from the f i l l i n g . The com bustion tu b e i s th e n sto p p ered * The system i s t e s t e d f o r le a k s by tu r n in g th e s to p cock so t h a t n e i t h e r a i r o r oxygen e n t e r s th e system . I f th e a s p i r a t o r c o n tin u e s to d r i p , a le a k e x is ts * When th e f i r s t s ig n s o f b u rn in g a r e n o te d th e combus t i o n sh o u ld p ro ceed slow ly and s t e a d i l y . The carbon d io x id e should be g e n e ra te d w ith s u f f i c i e n t speed to cause th e so d a- lim e to become q u ite warm, b u t n e v e r so r a p id ly t h a t th e a b s o rp tio n tube becomes u n co m fo rtab le hot* The a re a in which the h e a t i s g e n e ra te d i n th e a b s o rp tio n tube sh o u ld n o t ex ten d beyond the f i r s t p o r tio n of th e tu b e and sh o u ld n ev er sp rea d to t h a t s e c tio n o f the so d a-lim e which i s im m ediately a d ja c e n t t o th e calcium c h lo rid e l a y e r , When th e so d a -lim e tu b e b e g in s to e o o l, the b u rn in g o f th e su b sta n c e may be c o n s id e re d co m p lete, b u t th e combus t i o n i s c o n tin u e d f o r f iv e m in u tes lo n g e r to in s u re th e rem oval o f th e l a s t t r a c e s o f carbon d io x id e . The average tim e f o r a com bustion i s tw enty m in u te s. The oxygen o f th e a b s o rp tio n tu b e s sh o u ld , a c c o rd in g to P r e g l, be re p la c e d by pure a i r . V e tte r3, s u g g e s ts th a t i t i s in some ways b e t t e r to weigh th e a b s o rb in g v e s s e ls f i l l e d Y e tt e r , nM ic r© a n a ly tic a l Methods Tor th e in d u s t r i a l Laboratory,** Ghem A bs. XOT (1 9 3 2 ), 41, 22 w ith p ure oxygen, A ‘he d i f f u s i o n th a t ta k e s p la c e d u rin g the tim e th e a p p a ra tu s is b e in g weighed does n o t cause a p p r e c i a b le e r r o r s . I t i s n e c e s s a ry t o run b la n k t e s t s in o r d e r to in s u re t h a t th e a p p a ra tu s i s w orking s a t i s f a c t o r i l y , and a ls o in o rd e r to d e t e c t any d e f e c t s . A b la n k t e s t i s c a r r i e d out in e x a c tly th e same m anner a s an a n a ly s is w ith o u t a b o a t, fh e w eight o f th e a b s o rp tio n tu b e s s h o u ld be reproduced w ith a co n stan cy o f 0.005 mgm. F t & 5 ~ M i c p o - D u m p $ A p p a r a t u s f o p D e t e r m l n r t l o n o f N i t r o g e n A “ K I P P G E N E R A T O R B ~ C O M B U S T / O N T U B E C - F U R N A C E 0 ~ st o p c o c k e - MICRO-N/TROME TER F - LFVELING BOTTLE CH APTER IV GAS-VOLUMETRIC DETERMINATION OP NITROGEN IN MINUTE AM OUNTS OP ORGANIC MATERIALS. iMICRQ-DUMAS METHOD).1 A method o f d e te rm in in g n itr o g e n , in which a volume o f g a s was o b ta in e d o n e -te n th of which had alw ays to be d e d u c te d i n o r d e r to o b ta in a c o r r e c t n itr o g e n v a lu e , was d e s c rib e d by P r e g l in h i s e a r ly p a p e rs in q u a n t i t a t i v e m ic ro - a n a ly s is o f o rg a n ic compounds. T his e x c e ss in the volume o f g as was f i r s t a s c r ib e d to th e space ta k e n up by th e 50 p e r c e n t p o ta ssiu m h y d roxide s o lu tio n ad h e rin g to th e w a lls o f th e n itr o m e te r o r m ic ro a z o to m e te r. L a te r P r e g l h im s e lf proved t h a t th e c a u s tic p o ta s h occupied only 2 p e r c e n t (1 .7 per c e n t) o f th e m easured volume, The " in e v ita b le " e ig h t p e r c e n t was due to carb o n monoxide and to o th e r a s s o c i a te d g a s e s . T his was proved by c o l l e c t i n g th e gas over d i l u t e b lo o d s o l u t i o n r a t h e r th a n o v er c a u s tic p o ta s h . The carbon m onoxide-haem oglobin r e a c tio n was t e s t e d w ith hydrogen s u l f i d e s o lu t io n , P r e g l concluded t h a t " a p a r t from to o s h o r t a p e rio d of c o n ta c t betw een th e co m b u stib le g a se s and v ap o rs and th e r e d - h o t tu b e f i l l i n g , th e in c r e a s e o f th e gas volume o b ta in e d m ight a ls o be p a r t i a l l y due to the a c tio n o f th e red u eed copper s p i r a l . " He proved t h i s in an ex p e rim e n t. In a l a t e r experim ent he found t h a t th e in tr o d u c tio n o f copper l p . P r e g l, Q u a n tita tiv e o rg a n ic M ic ro a n a ly s is , p . 72, 25 a f t e r th e red u ced copper would o x id iz e th e carbon monoxide and e lim in a te t h i s e rro r* D uring th e com bustion o f o rg a n ic s u b sta n c e s n i t r o u s oxide may a l s o be form ed, ‘ i’he a n a l y t i c a l r e s u l t s a re n o t a f f e c t e d , a s th e n itr o u s o xide o cc u p ies th e same volume a s th e n itr o g e n which i t c o n ta in s . At a h ig h te m p e ra tu re , how e v e r, n i t r o u s oxide w i l l d is s a a s o c ia te in to n itr o g e n and oxygen and th e volume i s in c re a s e d one and a h a l f tim e s . M e ta llic copper i n th e h o t t e s t p a r t o f the tube would te n d to ab so rb th e oxygen produced. By u sin g a f i l l i n g which p re v e n ts th e p ro d u c tio n o f an adm ixture o f u n d e s ira b le g a s e s , and by o b se rv in g th e nec e s s a r y minimum time o f c o n ta c t of th e o rg a n ic v ap o rs to be red u ced copper s p i r a l i s in tro d u c e d in to a sm a ll com bustion tu b e , and the a i r is r e p la c e d by carbon d io x id e from a Kipp g e n e ra to r , d u rin g w hich p ro c e ss th e co p p e r s p i r a l i s h e a te d in o r d e r to make c e r t a i n t h a t a l l ab so rb e d g a se s a r e removed. J-he s p i r a l i s th e n allow ed to cool i n th e c u r r e n t o f carbon d io x id e , i f th e m ic ro z o to m e ter i s now a tta c h e d to th e com bustion tube i t w i l l be observed t h a t th e r i s i n g b u b b les o f earbon d io x id e d is a p p e a r, a p a r t from an alm o st i n v i s i b l e r e s id u e . As soon, however, a s the b u rn e r i s once more p la c e d below th e copper s p i r a l the ascen d in g b u b b les become l a r g e r , and in t h i s m anner m easurable q u a n t i t i e s o f gas can be c o l l e c t e d i f th e d u r a tio n of th e ex perim ent i s s u f f i c i e n t l y lo n g . G le a rly th e phenomenon i s due to a perm anent d is tu rb a n c e o f th e q u ilib riu m betw een carbon d io x id e on th e one hand and carbon monoxide and oxygen on th e o th e r , cau sed by th e r e d -h o t copper s p i r a l . A ll copper s p i r a l s a r e n o t e q u a lly a c tiv e in t h i s r e s p e c t. A p p aren tly th e phenomenon i s m ainly caused by c e r t a i n im p u r itie s in th e copper yfoich vary in am ount, p erh ap s by z in c . . . . . . *i*he r e s u l t s o f th e ex p erim en t a r e , how ever, q u ite d i f f e r e n t i f a c o n s id e ra b le q u a n tity o f co p p er oxide i s p la c e d in f r o n t o f the mass of m e ta l lic copper in such a manner t h a t th e p o r tio n a d ja c e n t to th e o u t l e t fo r th e c u r r e n t o f carbon d io x id e e x te n d s beyond the h e a tin g fla m e s , f h i s arrangem ent e n s u re s a te m p e ra tu re f a l l a t t h i s p o in t w hich c a u se s th e com plete o x id a tio n of the carbon monoxide which is form ed. 26 b u rn t w ith th e h e a te d tu b e f i l l i n g , th e volume o f n itr o g e n can be determ ined by u s in g a c o r r e c tio n o f two p e r c e n t of th e volume. Kipp G en e ra to r fhe carbon d io x id e used f o r th e v o lu m e tric d e te rm in a t io n o f n itr o g e n i s d e liv e r e d by a Kipp g e n e r a to r (A o f F ig . 5) which h as been allo w ed to sta n d f o r two o r th r e e days a f t e r i t h as been f i l l e d , xhe m iddle b u lb i s com p l e t e l y f i l l e d w ith m arble ch ip s which have been e tc h e d w ith h y d ro c h lo ric a c id and washed w ith w a te r. k q u a l p a r t s o f co n een tirated mGI and w ater are in tro d u c e d through th e u p p er bulb u n t i l th e lo w er b u lb and h a l f o f th e u p p er bulb a re f i l l e d , when th e sto p -c o c k o f th e m iddle b u lb is opened carbon d io x id e w ill e x p e l th e a i r . f h e a i r in t h e a c id o f th e u p p er bulb i s removed by the carbon d io x id e which i s g e n e ra te d when a few p ie c e s of marble a re dropped in to th e "S. b u lb . xhe carbon d io x id e i s d e l iv e r e d to th e com bustion tu b e th ro u g h a t h ic k w a lle d c a p i l l a r y tu b in g b e n t i n an in v e r te d Z sh ap e, sh e ta p e r e d end of th e c a p i l l a r y is f i t t e d in to th e mouth o f th e com bustion tu b e by means of a ru b b e r sto p p e is uombusti on rube and F i l l i n g A com bustion tu b e s im ila r to t h a t used f o r the d e t e r m in a tio n o f carbon and hydrogen i s u se d . A wad o f f r e s h ly ig n it e d a s b e s to s i s p re s s e d i n t o th e sm a ll end o f th e tube 27 and i s follow ed, by 120 mm. o f w ire -fo rm copper o x id e . T his i s h e ld in p la c e w ith a s b e s to s . About 40 mm. le n g th of th e copper oxide i s slow ly red u ced by h e a tin g in a stre a m of hydrogen washed w ith a c id perm anganate* The whole i s th e n allo w ed to c o o l i n a c u r r e n t o f hydrogen, The tu b e i s h e a te d and allow ed to c o o l in an atm osphere of carbon d io x id e b e fo re u s in g f o r th e f i r s t tim e, When n o t in u se th e tu b e i s l e f t co n n ected to th e g e n e ra to r and i s k e p t f i l l e d w ith carbon d io x id e u n d e r p re ssu re * T h is perm anent f i l l i n g i s fo llo w ed by a f i l l i n g which i s renewed fo r each a n a l y s i s , W ire-form copper oxide i s i n tro d u c e d u n t i l a l a y e r of 90 mm. i s formed* This i s fo llo w ed by th e weighed sample which h as been in tim a te ly mixed w ith copper oxide and th e n a 40 mm. la y e r o f co arse copper oxide com pletes th e f i l l i n g . M easurement o f N itro g e n The p r e c i s i o n m ic ro a zo to m ete r a s b u i l t fo r P re g l m easures the volume of a gas a c c u r a te ly to th e 0 ,0 1 c c . and w ith th e a id of a re a d in g g la s s th e volume can be e s tim a te d to 0*001 o c. The m ic ro a zo to m ete r and le v e li n g b ulb a r e c le a n e d w ith s u lf u r ic - e h r o m ic a c id and r in s e d r e p e a te d ly w ith w ater and allow ed to d r a in . P ure m ercury i s in tro d u c e d in t o th e n itr o m e te r so a s to cover th e opening o f the tu b e from the com bustion system and u n t i l i t i s a l i t t l e below th e opening o f th e tube le a d in g to th e l e v e l i n g b o ttl e * The 50$ p o tta s s iu m hydroxide s o l u t i o n i s p re p a re d by d is s o lv in g KQH in w a te r and adding a few g r a in s o f barium 88 h y d ro x id e , A f te r s ta n d in g f o r about f i f t e e n m inutes th e barium ca rb o n a te i s f i l t e r e d o f f . T h is p re p a re d s o lu t io n w i l l n o t foam and i s s to r e d i n b o t t l e s w ith ru b b e r sto p p e rs* Course o f A n a ly sis Carbon d io x id e flo w from th e Kipp g e n e r a to r i s ad ju s te d u n t i l m inute b u b b les (m icro -b u b b les) r i s e a t the r a t e o f one o r two p e r seco n d . The system is swept w ith COg b e fo re com bustion o c c u rs . Combustion should talc© p la c e slo w ly and ab o u t tw enty to tw e n ty -fiv e m in u tes sh o u ld e la p s e b e fo r e th e d e te rm in a tio n i s co m p lete. The a z o to m e te r i s disconnected*w hen the l e v e l in g b ulb i s s l i g h t l y r a i s e d , so as to p re v e n t a i r e n te r in g th e a z o to m e te r. The c o n te n ts o f th e az o to m e ter a re b ro u g h t t o app ro x im a te ly atm o sp h eric p r e s s u r e w ith th e le v e li n g b u lb . Tem p e r a tu r e e q u ilib r iu m i s e s t a b li s h e d in te n to f i f t e e n min u t e s , and re a d in g s a r e ta k e n o f th e te m p eratu re and o f the gas volume. Two p e rc e n t o f th e volume o f n itr o g e n found m ust be v d ed u c ted in o rd e r to allo w f o r th e space ta k e n up by th e 50$ c a u s t i c p o ta s h s o lu t io n . CH APTER V, EXPERIMENTAL LATA CARBON AND HYDROGEN In o rd e r to d eterm in e th e e o n s ta n t e r r o r t h a t would he p r e s e n t due to th e method and a p p a ra tu s a s e r i e s o f b la n k ru n s were made in which a l l th e c o n d itio n s were the same as f o r th e a c tu a l r u n s . However, no sample was in tro d u c e d . The c o r r e c tio n s as d eterm in ed a r e shown in th e fo llo w in g t a b l e s . A n e g a tiv e c o r r e c t io n shows an in c re a s e in w eight o f th e a b s o rp tio n tu b e and should be s u b tr a c te d from th e t o t a l w e ig h t. A p o s i t i v e c o r r e c t io n i n d ic a t e s a l o s s o f w eight and should be added. T ab le A. C o rre c tio n s f o r A b so rp tio n Tubes a s D eterm ined by- Blank Runs U sing M oist Soda Lime and Calcium C hloride in th e A b so rp tio n T ra in . B lank C o rre c tio n f o r C o rre c tio n f o r GOg Tube in mgm. HgO Tube in mgm. 1 + Q.055 - 0*23? 2 - 0 .0 7 6 - 0 . 1 2 6 3 - 0 .1 0 8 - 0 .1 7 8 4 + 0 .0 0 3 - 0 . 2 2 4 5 +0.036 - 0,170 Average - 0 .0 1 8 -0 * 1 8 7 T ab le B. C o rre c tio n s f o r A b so rp tio n Tubes a s D eterm ined by Blank Runs U sing D e s s lc a te d Soda Lime and Calcium C h lo rid e i n th e A b so rp tio n T ra in , B lank C o rre c tio n f o r C o rre c tio n f o r COg Tube i n mgm, HgO Tube in mgm. 1 - 0,037 " 0 ,1 6 3 2 - 0 . 0 4 2 - 0 .2 1 3 3 + 0 .0 4 0 - 0 .1 9 7 Average —0 .0 1 3 -0 * 1 9 1 30 T able I* R e s u lts o f a S e r ie s of M icro-C om bustions i n Which M oist Soda Lime and Calcium C h lo rid e Were Used i n th e A b so rp tio n Tubes, Sample 1 3 3 S u b stan ce Weight o f Weight o f Weight o f Weight o f a n a ly z e d sample in GQg found HgO found HgO found grams in grams i n grams c o r r e c te d s u c ro se su c ro se s u c ro se ,004735 .004642 .007297 .007166 .007277 ,004651 P e rc e n ta g e by Weight .002937 ,002716 *002967 ,002750 .002529 .002780 Carbon Sample Found * C alcu l a t e d $ E rr o r * Found U n co rr. * Found C o rr, % C alcu l a t e d * E rro r * 1 42,00 42,08 0 .2 6 .9 4 6 .5 0 6 .4 8 0 .3 2 4 2 .0 8 42,08 0 ,0 6.54 6.08 6.43 6 .1 3 42*67 42.08 1 ,4 7 ,1 3 6.69 6,43 3 .2 T able I I . R e s u lts o f a S e r ie s o f M icro-C om bustions in Which D e sic c a te d Soda Lime and Calcium C h lo rid e Were Used in th e A b so rp tio n Tubes. Sample S u b stan ce Weight o f W eight o f Weight of W eight of a n a ly z e d sam ple in COg found HgO found HgO found gram s. in gram s, in gram s, c o r r e c te d 1 2 su c ro se s u c ro se .004237 ,004116 ,006549 ,006386 .002538 ,002405 .002347 .002214 P e rc e n ta g e by Weight Carbon Sample Found C alcu l a t e d E r r o r Found U n co rr, Found C orr, C aleu l a t e d $ h % $ 1° 1 42,15 42,08 0 ,2 6.70 6.20 6 .43 2 4 2 .3 1 4 2 .0 8 0 .5 6 ,5 3 6 .0 2 6.48 E r r o r 4 ,3 7 .0 31 T able I I I . R e s u lts o f a S e r ie s o f M icro-C om bustions o f an Unknown O rganic Compound in Which D e s s ic a te d Soda lim e and Calcium C hloride Were Used in the A b so rp tio n Tubes. Sample 1 2 3 W eight of sam ple in grains ♦Q04234 .003973 ,004274 W eight o f COg found i n grams .009698 .009472 ,010236 W eight o f HgO found i n grams .002408 .0 0 2 2 2 1 .002315 Weight o f HgO found c o r r e c te d ,002217 .002030 .002124 P e rc e n ta g e by Weight Carbon Sample $ Pound $ E rro r 1 2 3 62,46 6 5.01 65.31 4 ,4 0,6 0.1 $ Pound U n co rr. 6 .3 6 6 .2 5 6 .3 1 Hydrogen Found C orr. 5 .8 5 5 .7 1 5.56 $ E r r o r 6 .3 3 .8 1.0 The co m p o sitio n o f t h i s unknown was l a t e r found to be G^HgOg o r hydroquinone. The c a lc u la te d p e rc e n ta g e o f carbon i n hydroquinone i s a p p ro x im a te ly 6 5 .4 ; hydrogen i s 5 .5 . The av erag e p e r c e n t e r r o r is 2 .7 $ f o r carbon and 3 .7 $ f o r hydro gen. 22 N itro g e n A c o r r e c t io n o f 2$ o f th e volume i s made f o r th e v o l ume occupied hy th e 50$ KOH s o lu t io n . The w eig h t o f n i t r o gen a t s ta n d a rd c o n d itio n s i s ta k e n to "be 1*2507 m illig ra m s . Table IV. R e s u lts o f a S e r ie s o f Micro-Dumas D e te rm in a tio n s o f A c e ta n ilid e i n Which 50$ C a u stic P o ta sh S o lu tio n Was Used i n th e M ic ro -N itro m e te r. Sample Weight sample mgm. Of in N itro m e te r re a d in g in m l. B arom eter re a d in g P re s s u re c o r r e c te d Temper a t u r e C. 1 8 .0 5 4 .742 756.8 754.11 22 2 7.733 ,715 756.8 754*11 22 3 7 .455 .695 756.8 754.11 22 4 7.180 • 658 755.4 752.76 21.5 5 7.439 .690 755.4 752.76 21.5 P e rc e n ta g e hy Weight Sample V ol. o f Ng $ Ng Pound $ N« Theo r e t i c a l $ E rr o r 1 ,6676 10.43 10.37 0 .5 2 .6437 10.41 10.^37 0 .3 3 .6253 10.49 10.37 1 .1 4 .5925 10.32 10.37 0 .4 5 .6216 10.44 10.37 0 .6 C H & PTEE 7 1 . SPECIAL CONSIDERATIONS U sing sam ples of l e s s th a n 5 m illig ra m s a s l i g h t e r r o r i n th e w eight o f a b s o rp tio n tu b e s is m a g n ifie d . I f 2,727 mgm. o f m a te r ia l are u se d , th e n 0 .0 1 mgm, o f carbon d io x id e c o rre sp o n d s t o 0 ,1 p e r c e n t o f carbon* The l a r g e r th e sample th e s m a lle r w i l l be th e e r r o r which i s due t o e x p e rim e n ta l te c h n iq u e . E r r o r s may be o b serv ed when th e a p p a ra tu s i s f i r s t s e t up and f i l l e d , which a p p a re n tly d im in is h w ith u s e . T h is i s e s p e c i a l l y tr u e i f the ru b b e r c o n n e c tio n s have n o t been cu red by one o f th e m ethods d e s c rib e d . Uncured ru b b er te n d s t o g iv e o f f g a se s which g iv e an in c re a s e d w eight to th e soda lim e tu b e . The u se of th e a s p i r a t o r keeps the g a s flo w in g s t e a d i l y and in some m easure p re v e n ts such e r r o r s . The v e l o c it y o f the g a s c u r r e n t may a ls o in tro d u c e an - e r r o r . I f th e oxygen i s p a sse d too r a p i d l y th ro u g h the com bustion tu b e , in co m p lete o x id a tio n o f th e carbon may r e s u l t and a lo s s o f w eight w i l l be found i n th e soda lim e tu b e . The r a t e o f oxygen flow should n o t be o v er t h r e e c u b ic c e n tim e te rs p e r m inute and in th e case o f a h ig h carbon c o n te n t even t h i s r a t e sh o u ld be d e c re a s e d . The u se o f a lo n g e r com bustion tu b e or th e in tr o d u c t io n o f o th e r c a t a l y s t s such as p l a t i n i z e d a s b e s to s w i l l allo w a g r e a t e r gas v e l o c i t y , A f r e s h l y f i l l e d com bustion tu b e must be h e a te d 34 c o n s ta n tly fo r tw enty hours b e fo re a c o n s ta n t b la n k t e s t can he o b ta in e d , A p ro p e rly f i l l e d com bustion tu b e w i l l l a s t for 200 to 300 a n a ly s e s . A c o n s ta n t in c re a s e i n w eig h t o f th e calciu m c h lo r id e tube d u rin g b la n k ru n s allo w s f o r th e c a l c u l a t i o n of a c o r r e c t i o n f o r th e b la n k . The s l i g h t f l u c t u a t i o n i n th e w eight o f the soda lim e tu b e , now l o s i n g w e ig h t, now g a in in g does n o t p e rm it th e use o f a c o r r e c t io n . The m a te r ia l s u sed i n th e a b s o r p tio n tu b e s sh o u ld be from th e same l o t a s th o s e u sed in th e d ry in g t r a i n . The d eg ree o f d ry n e s s o f t h e g as e n t e r in g th e com bustion tu b e must be eq u a l t o t h a t o f th e g as which le a v e s th e a b s o rp tio n tu b e . As a r e s u l t o f th e e x p e rim en ts com pleted, th e 20 mesh ca lciu m c h l o r id e and soda lim e i s recommended. In c o n s id e r in g th e d a t a o f T ab le s I and I I th e r e does n o t seem to b e any d if f e r e n c e in the a b s o rp tio n of carb o n d io x id e by d ry soda lim e and by soda lim e c o n ta in in g a b o u t m o is tu re . CHAPTER V II. CONCLUSIONS 1. In t h i s stu d y an i n v e s t i g a t i o n was made of a l l o f the a v a i l a b l e l i t e r a t u r e d e a lin g w ith q u a n t i t a t i v e o rg an ic m ic r o a n a ly s is . S p e c ia l c o n s id e r a tio n was g iv e n to th e d e t e r m in a tio n of ca rh o n , hydrogen and n itr o g e n . The d ry combus* t i o n , o r th e P r e g l m icro-m ethod w ith c e r t a i n m o d if ic a tio n s of a p p a ra tu s and method was s e le c te d f o r th e d e te rm in a tio n of carbon and hydrogen. The micro-Dumas method was s e le c te d f o r t h e d e te rm in a tio n of n itr o g e n . 2. A pparatus was c o n s tru c te d f o r th e d e te r m in a tio n o f carbon and hydrogen and was cheeked by b lan k ru n s and w ith a s u b sta n c e whose co m p o sitio n was known. The co m p o sitio n o f an unknown compound was a l s o d eterm in ed . 3. A lthough th e sam ples used were l e s s th a n f iv e m illig r a m s * carbon was d e te rm in e d w ith in 0 .4 6 p e r c e n t o f e r r o r j hydrogen was d eterm in ed w ith in 4 .1 8 p e r ce n t o f e r r o r , o r 0.46 p e r c e n t h ig h and 0 .2 1 p e r c e n t low . T his a c c u ra c y i s g r e a t e r th a n t h a t u s u a lly o b ta in e d in th e average m acro- eom bustion. 4 . The a p p a ra tu s was m o d ifie d in o rd e r to d eterm in e th e p e rc e n ta g e of n itr o g e n i n a known s u b s ta n c e , n itr o g e n was d eterm in ed by th e micro-Dumas method w ith in 0*54 per c e n t o f th e t h e o r e t i c a l . 5 . M icrochem ical methods p r e s e n t many ad v a n tag e s over th e o ld e r and slow er m acro-m ethods. The economy o f tim e and 36 m a te r ia l s p o s s ib le th ro u g h the use o f th e s e methods p e rm its th e u se o f more e x p e n siv e m a te r ia l s and ap p a ra tu s* th e r e d u c tio n o f space g iv e n to l a b o r a t o r i e s , and th e e lim in a tio n o f te d io u s h o u rs o f r o u tin e com bustion. BIBLIOGRAPHY A bderhalden, E . , Handbueh d e r biochem ischen A rb e itsm eth o d e n . V ol. V, 1307-1356. A very, S ., B raehenbury, J . and M aclay, W.D., "Ih e M etal lu b e in M icro- and Sem i-m icrocom bustion A n a ly s is ." In d . Eng. Gfaem. . A nal. E d ., Vol. XV, 238-9, 1932. B a ile y , J .R ., "Loading Combustion !Eube i n uarbon and Hydro gen D e te rm in a tio n on L iq u id s ." In d . Eng. uhem. , A nal. E d ,, v o l. V, 17, 1933. B eh re n s-K ley , Q rganlsche M ikro-chem ische A n aly se. L epold V oss, L e ip z ig , 1922. 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F la s c h e n tr a g e r , B ., "E x p erie n ces i n O rganic M ic r o a n a ly s is ," Z. angew. Chem. . V ol. XXXIX* 717-22, 1926. O jA ., XX, 2802, 1926. F r e r i , M ., "fh e D e te rm in a tio n o f Carbon and Hydrogen by the M ic ro a n a ly tic a l Method of F r i t z P r e g l a p p lie d to Explo s iv e L i q u i d s ." Gazz. chlm. i t a l . , V ol. LX II, 606-9, 1932. C .A ., XXVII, 41, 1933. F r i e d r i c h , A ., "M ic ro d e te rm in a tio n s of Carbon and Hydrogen by th e Method of F r i t z P r e g l . tf M ikrochem le, V ol. I l l , 2 0 -6 , 1931. C .A ., XXV, 1182, 1931. .F r ie d r ic h , A ., " C o n trib u tio n s to the Technique o f the Q uant i t a t i v e M ic r o - a n a ly tic a l D e te rm in a tio n o f Carbon and Hydrogen by th e F r i t z P r e g l M ethod," Z. angew. Chem. , V ol. XXXVI, 481-2, 1923. C.A. , XVII, 29, 1924. F r i e d r i c h , A ., "Hew Technique f o r Combustion in Mi cro ch em ical E lem entary A n a ly s is ." Z. angew. chem. , XIV, 476-8, 1932. C .A ., XXV, 1182, 1931. C^A., XXVI, 4767, 1932. F r i e d r i c h , A ., " M ic r o - a n a ly tic a l D e te rm in a tio n o f Carbon and H ydrogen.” M ikroohem ie, V ol. IV, 329-54, 1931. C.A. , XXVI, 46, 1932. G arn er, W., "O rganic M ic r o a n a ly s is ." In d . C hem ist, V ol. V, 5 8 -6 1 , 1928, Gouben, R ., "E lem entary M ic r o a n a ly s is ," H etuvern L y d s o h r if t, V ol. X, 129-36, 1928. B u ll, so c . chim. b e l g . , Vol. XXXVII, 335-44, 1929. C .A ., XXI, 3576, 1927. C.A. , X X III, 789, 1929. G ran ach er, C ., "M icro -elem en tary A n a ly s is o f Compounds Con ta in in g S u lf u r , H alogen o r H itro G roups. The Double C om bustion." H e lv e tic a chlm ica a c t a , Vol. I I , 76-84, 1919• S«A ., X I I I , 822, 1919. Kemmerer, L . , a$d H a l l e t t , B ., "An Improved Method o f O rganic M ic ro -c o m b u stio n ." Knd. Eng. Chem. , V ol. XIX, 173-6, 1927, K irk , P . L . , and MeCaXXa, A. 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Creator Cosgrove, J. C (author)

Core Title A study of methods of quantitative organic microanalysis

Degree Master of Arts

Degree Program Chemistry

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