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Microchemical analysis of dust as an aid in the detection of crime

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Microchemical analysis of dust as an aid in the detection of crime

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Content MICROCHEMICAL ANALYSIS Of DUST AS AN AH) IN THE DETECTION Of CRIME A Thesis Presented to the faculty of the Department of Chemistry University of Southern California In Partial fulfillment of the Requirements for the Degree Master of Soienoe Nioholas R. Bondoo June 1935 UMI Number: EP41461 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 EP41461 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Dteertatten- PaMfeMng 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 48106-1346 This thesis, written under the direction of the candidate’s Faculty Committee and approved by all its members, has been presented to and ac cepted by the Council on Graduate Study and Research in partial fulfillment of the require ments for the degree of Master of Science Dean Faculty Committee Acknowledgment 3?h© writer wishes to express his appreciation to Dr. Paul H. M.-P. Brinton, teacher and scientist, who gives freely from a rich experience. TABLE OP CONTENTS SECTION PAGE I. STATEMENT AND IMPORTANCE OP PROBLEM......... I II. A BRIEF HISTORY OP THE PROBLEM............... 3 III. THE APPARATUS DEVELOPED FOR COLLECTING THE DUST PARTICLES ............... ....... 5 IV. ANALYSIS OP ROCK DUST SAMPLE . . ........... 9 Determination of silica......................11 Determination of alumina, etc........... . 13 Fusion with pyrosulphate .............. . 15 Determination of i r o n .............. 16 Determination of calcinm......................19 Determination of magnesium ................. 20 V, THE ANALYSIS OP MICRO METAL SAMPLE ...... 22 Discussion of sample ....................... 23 Determination of lead ................. 23 Determination of copper......................25 Determination of z i n o ................ 28 VI, THE ANALYSIS OF PLASTER SAMPLES ........... 31 VII. SUMMARY......................................... 38 BIBLIOGRAPHY ...................................... 39 LIST OF FIGURES FIGURE PAGE 1. Apparatus for collecting micro dust particles . 6 2# Units of sample collector .. .. .. ... .. 7 0. Improved sample collector . .......... 8-U 4. Apparatus for micro volumetric determination . 18 5. Apparatus for determination of copper ......... 26 6. Units of apparatus for determination of copper . . ..................................... 27 STATEMENT AND IMPORTANCE OF PROBLEM These studies and experiments have been conducted on the premise that through dust particles on one’s person some index of his habitat, or location at a given time, or of his occupation may conclusively be drawn. The value of such evidence if proven conclusively is self-evident. Bust particles are accumulated by an individual during his waking and sleeping hours. They come largely from his direct environment. It may be said that dust is as ever present as the air breathed, the soil underfoot, the tools and appliances used in everyday living, and the walls within which living takes place. It is then probable that under certain conditions these particles will often connect one with an object in question. While it is possible for an individual to rid him self of dust traces, and thus avoid detection, still the criminal frequently fails to realize his danger, so evidence from the microehemical analysis of dust is often of great importance. It is admitted that first rate evidence of this nature is at best circumstantial. But it is well also to keep in mind that in many cases circumstantial evidence has been more reliable than direct evidence. This is especially true in the face of perjured witnesses, inaccu- 2 rate observations of honest witnesses, and in all those cases wherein emotional factors are apt to overbalance factual evidence. At first it might seem that in order to connect a per son with a certain location by this method, it would be nec essary to know the composition of the entire country-side. . Such a knowledge is, however, not required of the investi gator. In almost every instance there is brought to the prob lem to be investigated a seat of the crime or occurrence. In the following work, micro analyses of rock, metal, and plaster have been carried out by modified macro chemi cal methods. In all cases the theory and reagents applied are standard, and consequently no special listings of re agents are given at the beginning of each analysis. The theory has been but briefly outlined, as detailed accounts may be found in suitable books. There has been some vari ation in technique used here, as compared with the general macro technique. This variation is described under the individual analyses. The size of the samples chosen has been within the range ordinarily considered as "dust". The balance used for these determinations was the "Becker Micro-Chemical Balance". The theoretical accuracy of this instrument is 0,001 milligram, and the samples chosen fell well within the range of the scale. A BRIEF HISTORY OF THE PROBLEM1 It would "be an error to believe that the idea of studying dust for the purpose of discovering criminologi cal evidence is of modern origin. By searching diligently we may trace it to the old masters of legal medicine. The first author to clearly describe cases where this type of research was used was Hans Gross. In his manual for ex amining magistrates, Gross grouped together everything in these various teachings that would contribute to the build ing up of a good criminal investigation. It is indeed sur prising when reading his volume today to discover that, in spite of the progress that has since been made in this field, the ideas, or at least the germ of them, was already found in Gross' works. The next occurrence of this sort of investigation is picked up in the works of a popular novelist. Conan Doyle, before becoming an author, was an earnest student of medicine. At Edinburgh he was a pupil of Joseph Bell, ah old army surgeon and hospital physician, who taught him in addition to the solid principles of legal medicine the art of analytical reasoning, in which he excelled, iFor a more extensive sketch see Edmond Locard, The American Journal of Police Science. 1, 278 (1930), Horth Western University Press, Chicago Illinois. Others who have studied the issue at later dates include Edmond Docard? whose articles appeared in this country in the American Journal of Police Science from May to August, 1930. Still other investigators are at tacking the same problem* Gieseehe and Papps have pub lished some remarkable observations on dust which they have collected and analyzed* Severin Icard, of Marseilles, with the collaboration of Jean Maurel has made a special study of the dust retained by the cerumen of the external auditory canal, commonly known as ear-wax. Finally in 19£6 Dr. George Yuillemin, of Haney, devoted his inaugural thesis to an excellent review of the subject. ^ Edmond Loeard, Policieos de romains, et de labor- atoire. Paris, Payot, 19££. THE APPARATUS LEVELOPEL POE COLLECTING THE LUST PAETICLES When the first investigator along these lines, Hans Gross, undertook to examine dust he did it rather crudely. The clothing to he examined was placed in a large paper hag, which was securely closed. He then heat the hag with rods or heaters called "tapettes", which housekeepers used to clean draperies and upholstery. The dust extracted in this manner accumulated in the bottom of the hag, from which it had hut to he collected. Loeard recommends the following devices for accom plishing the task. For direct collection one may use flat pinchers or forceps, cataract needles, or better stillt he suggests that the spots he removed by moistening them. By the use of the apparatus illustrated in Figure 1, which was developed in the present research, another direct method for obtaining samples is offered. With it dust can he collected from almost any type of article. Vacuum is produced in the glass tube by the use of a com mon aspirator and running water. The second illustration shows the necessary parts, all of which are easily ob tained. The screen disc attached to the glass rod, as shown, allows a filter paper disc of the same size to he easily adjusted and withdrawn when the sample is collected. The rod and disc may he forced out of the tube, thus 'I I x f ' H V T V flercy/ttdo/T o A * f * &7'f /} SZ /J y i/ e ^/o'S'f w/f4 y/ass A/Ae £ 7 ^ y 7 ^ /c c / <Z?Z -es rc A . a*,/s. C o f f e r - yS' tr/ Tcer^ t S /s t r c ? /Z u c A e < A e ? r sAoujy^ A> jr/?sr /-oai 0 * / C m 9 > /AyZZxrs- j y * > f y o < ? / ~ %/ c^A^Ao/S". / » S~Z>A/ tZtAsypAorr Z '/y a ’A J*4,r / i'C a c rc Z ^ /j/a r- 3 „ C S a^J/e/osZ CZr&W/Ca/ /r&sm7*?^ l / f j f ' / s 0f K J c ? f T 7 / j / g Co/ ZeaZor : /Vtd/ro/o f A?/S>^/7c/o<L . 8 allowing the sample on« the filter paper to he taken out of the tube without shaking or tapping it. The samples when so obtained are easily examined under a microscope, or transfered to analytical beakers and crucibles. The ap paratus when used in this manner is efficient where the samples are abundant, but unsatisfactory where there are but traces of dust to be obtained. A modification of the same apparatus is shown in figure 3 which has been found entirely satisfactory for collecting very small samples. It is essentially the same in principle, but the filter paper is inserted dif ferently and it does not require the screen disc and glass rod unit. The filter paper when used in this manner is folded in the same way as when used with a laboratory funnel. The rubber stopper containing the adaptor is then forced into the tube, making the collecting cell almost dust tight. The apparatus, when used as described above in ob taining quantitative metal samples, proved one hundred per cent efficient, as was revealed by a microscopic ex amination of the cloth from which the dust was obtained. Other apparatus used in the 'actual analysis of the samples is described in later pages. yZtsoajf bc s/r n oyg ' 'C rc y z *s /{/s £ / ° / { / r '■ 0 /J ■£ XsyJvflS yjarr y ANALYSIS OF HOCK LUST SAMPLE 1 The rock analyzed was one known to contain silica, aluminium group, calcium, and magnesium. Because of the nature of the sample it was necessary to decompose the rock by fusion with anhydrous sodium carbonate. At the temperature of fusion this reagent decomposes the minerals present forming silicate, aluminate, phosphate, and zir- conate of sodium* and carbonate, silicate, and perhaps aluminate of iron, magnesium, calcium, and barium, all of which are soluble in hydrochloric acid. The sample was pulverized with a small mortar and pestle before the v/eighing took place. The sample was then weighed in a micro platinum crucible and was found to weigh 0.011011 grams. The crucible used was hardly 1 cm. high and perhaps .70 cm across the top. To the crucible containing the weighed sample was then added approximately 0.06 grams of the carbonate. This was ac complished by weighing the carbonate on glazed paper and then transferring it entirely into the orucible by means of a small camel's hair brush. The crucible was then placed above the flame, supported by a chromel triangle made small enough to hold the crucible and with long enough ^•Washington, The Chemical Analysis of Rooks, 4th edition. John Wiley and Sons, New York-. 10 arms to be supported by an ordinary ring stand. The heat was first supplied from a Bunsen flame at least 10 cm. be low the crucible. The flame was held at this position until all moisture was expelled. The crucible was then lowered and the flame adjusted to a faint red, and finally the mass heated to fusion at a dull red heat. The mass was kept in quiet fusion for at least thirty minutes, dur ing which time slow currents were observed crossing the red hot liquid. After the fusion the crucible and its contents were allowed to cool slowly. When the cake was thoroughly cool it was removed from the crucible. This was done by adding distilled water from a small wash bottle until the water line within the micro crucible was up to the one-third line. Some time was allowed for the v/ater to creep below the cake, and then it was cautiously heated by passing a gas flame back and forth below the crucible bottom. When the cake loosened it was entirely transferred into a 50 cc, beaker. The transfer was accomplished by holding the crucible on a glass rod over the crucible and directing a stream of water into it from a micro wash bottle, taking care to recover all washings. The 50 cc, beaker contain ing the cake and washings was only about half full. The cake was then dissolved in approximately 10 cc, of hydrochloric acid. The acid was cautiously added from a pipette so adapted as to allow the acid to run under a watch glass used to cover the beaker, These precautions were taken to avoid spattering or mechanical loss. In order to aid the solution it was heated on a water hath while the heaker remained covered. When all effervescence had ceased in the heaker, it was removed from the water hath and the drops on the watch glass washed into the heaker by means of a stream from the wash hottle. The solution in the heaker contained all the rock constituents in solution as chlorides, except the silica, most of which was in the solution as soluble sil icic acid and as insoluble particles. The next step was to render the silica insoluble and thus separate it from the other constituents so that it might he weighed, Determination of silica. The solution above was evaporated to dryness in the heaker on a water hath. The salts were then heated for one hour after the mass was dry, After cooling, the mass was moistened with a few drops of concentrated hydrochloric acid to dissolve the basic salts formed during the evaporation. Approximately 10 cc, of water was then added and the contents of the heaker heated over the water hath until the chlorides were all dissolved, leaving only the insoluble silica. The entire solution was then passed through a micro filter 12 using a glass funnel approximately 6 cm. long ana 4 cm. across the top. The filter paper was cut to fit into this funnel in the usual way. The solution was filtered and washed with about 8 ce. of water containing a trace of hydrochloric acid. The filtrate from the above was caught in a 50 cc. beaker and evaporated to dryness a second time. It was then treated exactly as- were the salts from the first evaporation. The combined residues were then treat ed further while the combined filtrates were reserved for further analysis. The silica residue and filter papers were then placed in the platinum crucible used earlier in the deter mination and carefully ignited to constant weight, using a Bunsen flame and the micro triangle. The weight so ob tained represented that of the crucible, plus s10g plus impurities, and was so recorded. The silica so obtained was then rid of the impur ities which it contained. Among these were AlgQg, EegOg, TiOg, and fg05. This was done by moistening the mass within the crucible with one or two drops of water and then with a like amount of 1:1 sulphuric acid. This was done to retain i^he TiOg which would otherwise volatilize. To this was then added a few drops of hydrofluoric acid. Enough of this acid was added to dissolve the silica on warming. The mass within the crucible was evaporated 13 above the Bunsen flame and in a good draft under a hood. It was then ignited to constant weight at bright red heat. The weight recorded represented that of the crucible plus impurities. The loss in weight represented that of silica which had been volatilised off during ignition. To this weight was added a small weight determined later in the analysis and due to soluble silica. The data so obtained follow: lit, of sample■» .011011 gr. Wt. of silica * .003790 gr. * .00379 x 100 . * .011011 * 34:.42 5® silica. Determination of Alumina. etc. To the filtrate from the silioa determination was added approximately 4 cc. of concentrated hydrochloric acid. This was done in order to form ammonium chloride on the addition of ammonia, the presence of which prevented precipitation of magnesia with the alumina and iron. At this point it was decided to co-precipitate manganese with the alumina. The reagent used was bromine, which investigators recommend very high ly, The liquid contained in a small beaker was colored with a drop of methyl red, Concentrated ammonia was then added slowly during which time the liquid was heated al most to boiling. Then approximately 2 cc. of bromine water were added, keeping the liquid alkaline by the simultaneous 14 addition of ammonia* The precipitate so obtained was filtered while hot through the micro filter and thoroughly washed with about 15 cc. of a Z f o solution of ammonium chloride* The filtrate and washings from the ammonia pre cipitation almost invariably contain traces of alumina and iron hydroxide. These are separated by reprecipita tion using the same method and reagents as used in the first precipitation. The combined precipitates are then treated to free them from any magnesia as well as lime and alkali chlorides, which may have been co-precipitated during the process. This xvas done by redissolving the precipitate with hydrochloric acid poured through the filter and reprecipitating the alumina, etc., as before. This was done cautiously so that no loss from either precipitate or filtrate occurred during the operation. Finally the ammonia precipitate was ignited to constant weight using the original platinum crucible. The heat ing was repeated at bright-red heat to constant weight. The weight so obtained is that of crucible plus AlgOg, etc. In this group are included total iron as Feg0g, TiOg, 3?g0g, Mn304t ZrOg, OrgOg, VgQg, the rare earths, and, of oourse, AlgOg. The weight obtained from this ignition follows: Wt. of sample = 0.011011 gr. Wt, of ppt. s 0,005791 gr. 15 • 0,005791 x 100 . € • * 0.011011 " 52»57 7 > AlgOg. Fusion with pyrosulphate. Because further deter minations in the alumina group y/ere to be made* the pre cipitate obtained was again brought into solution. Shis was accomplished by adding about 0.07 grams of potassium pyrosulphate to the crucible containing the AlgOg precip itate in a manner similar to that used in the carbonate fusion. The mixture was then carefully heated at red heat, taking special care in the heating not to lose any of the material by way of spattering. When no undissolved sub stance could be seen in the crucible the flame was removed and the mass allowed to cool. After the cooling the en tire cake was transferred to a clean 50 cc. beaker, as previously discussed, and dissolved in approximately 20 cc. of water slightly acidified with sulphuric acid. It was found that the entire cake dissolved in this amount of water plus a few cc. of wash water, with the exception of a trace of silica, which was recorded with the main portion of that element. The solution obtained from the pyrosulphate fusion was used to determine the total iron oxides. Although the solution contained several other elements none was determined. This was done because the iron results ob tained were at best 6.51 % off. Because the calculations 16 to be used in further determinations in this group were to be based on difference, it was felt that they would be insignificant, since this type of calculation must have a correct basis from which to start. Determination of iron. The filtered solution of the mixed sulphates from the above contained all the iron in the ferric state. In order to titrate with potassium permanganate all of this had to be in the ferrous state. The reduction was accomplished by placing the entire sol-* ution in a 60 cc. Irlenmeyer flask and passing washed hydrogen sulphide directly into the flask. When the iron was found to be entirely reduced, the solution was heated gently while carbon dioxide was introduced into the flask. This was done to rid the solution of hydrogen sulphide, which if present would reduce the permanganate solution. When no more hydrogen sulphide was present as evidenced by the lead acetate paper test, the flask was corked and was ready for titration. The liquid was then titrated with potassium per manganate from a microburette. The results from this titration were found to be very high. Perhaps this was due to extreme dilutions which made the delicate end point indistinguishable. It was found also that the rubber tubing used when hydrogen sulphide was being 17 generated held some of the gas within it which could not be expelled even when the generator was producing carbon dioxide. To avoid this during a second determination, separate tubing was used for each gas generated. A special apparatus was also developed to in some way compensate for the end point difficulties. The theory upon which the writer developed the apparatus is that color tints may be more readily observed through a deep column of liquid placed on a white background. The apparatus is illustrated in Figure 4, and the function of the cap shown is that of shielding the surface of the liquid in the tube from the reflection of the permanganate in the burette above, and at the same time allowing the observer to watch the reaction within the tube. The best results were ob tained when the reduction was carried out as above and when this apparatus was used. The results obtained follow: First sample Second sample (without apparatus) (with apparatus) Wt, of sample z 0.011011 Wt. of sample = 0.014932 oc. of .01118 EMn04 = 7.8 cc. .01118 EMn% = 4.2 7.8 x .01118 x ,078 x 100 . . 4.2 x .01118 x .078x 100 _ — ^Oiloii bU,b/a* ,014932 24.4 f o FegOg. Something happened to the first determination that made the result entirely illogieal, but for the sake of completeness it is included. While the results obtained using the 19 apparatus shown and other precautions mentioned, were closer to the true value than those first obtained, neither was satisfactory. Iron may be determined quite satisfac torily, in micro quantities, colorimetrically, butthe oc casion might easily arise where an accurate volumetric method would be of value. Thus more work based on this previous ivork might profitably be done. Determination of calcium. For this analysis the filtrate from the ammonia precipitation was used. The sol ution, contained in a 100 cc. beaker, was brought to gentle boiling, and approximately 5 cc. of a saturated solution of ammonium oxalate was slowly added from a test tube. During the addition of the oxalate, the boiling solution was constantly stirred, and then it was allowed to settle over night. The solution was filtered through a micro filter, catching all of the filtrate and washings in a 150 cc. beaker. The preoipitate was then redissolved and caught in a 50 cc. beaker, where it was repreoipitate$, using the method and amounts of reagents stated above. The final precipitate was washed with several cubic centimeters of ammonium oxalate solution. The precipitate was placed in the micro crucible and ignited to constant weight at bright red heat. The residue so obtained was calcium oxide and was calculated in percentage as follows: t TTT ■ “f ■ / / ( o ~(^/y C <S />^ S ' £ - V 7 7 * /o/O -/i> < . //srrsria yL'/^ u s / ' / / r j / 5 n ? 6 S S 7 c / y?&S' i V yf^s&zzcy^, yfyy^’ j ' / z z A / S ' s/ A y y ' C ' r ' 0 l/ o/ ^zr^ yy/ C ■^y&£! ‘ s ' S 7 7 * / ? a / y a r ^ . T* 20 Wt, of sample « 0.011011 gr. Wt. of GaO * 0.001264 gr. • 0*001264 x 100 _ AQ a - n • * 0.011011 " *49 % CaO. Determination of magnesinm. The filtrate from the calcium determination was used for this estimation, To the solution contained in the 150 oo. beaker was added approximately 8 co. of ammonia. This amount alkalized the solution. Then about 10 ee. of a filtered solution con taining 3 grams of sodium ammonium phosphate in 50 cc. of water were slowly added to the cold solution. The mixture was well stirred and allowed to settle over night. At the end of this time the solution was passed through the micro filter and washed with 5 $ ammonia water. The entire pre cipitate was then redissolved in warm dilute hydrochloric acid and caught in a small clean beaker in which it was repreeipitated. The reprecipitation was brought about by adding ammonia to alkalinity, as shown by a drop of methyl red, with constant stirring. When the precipitate was well formed a few drops of ammonia were added and the mixture was allowed to stand over night. The final precipitate was collected on the micro filter and ignited in a por celain micro crucible, slowly at first, and then at red heat, to the pyrophosphate. The results obtained appear below, using the con version factor of MggPgOy to MgO as 0.3621: 21 Wt. of sample = 0,011011 gr. Wt. of ppt. s 0.001606 gr. 0.001606 , , x 0,36.81 X.10.0 ~ B 2Z % Mff0 0.011011 o,ao f o Mgu, Table of Analysis of Rook Dust Constituent f o by Macro f o by Micro Method2 Method SiOg 32.86 f o 34*42 f > A1203, etc. 46.99 f > 52.57 f o I'egOg 28.91 f o 22.40 % CaO 13.09 f o 11.49 f o MgO 5.84 f 5.23 f 2These results were obtained by Dr. R. B. Ellestad and Dr. Tohru Kameda, of the Laboratory for Geological Rock Analysis, in the University of Minnesota. Thanks to them is hereby expressed for furnishing this analyzed sample. THE AHALYSIS Of MICRO METAL SAMPLE Anyone working metals with a saw or file would he almost certain to get some amounts of fine metal dust on his clothing. This dust would collect particularly on the sleeve cuffs and on the trousers above the knees if one were sitting aown while filing. It can he readily seen that in the case of a counterfeiter or a key maker the an alysis of the metallic dust found on the clothes might he a very valuable aid in establishing the recent activities of a suspected person. This analysis was undertaken, having been given a sleeve of a coat which contained metal filings. The filings were scattered throughout the material in a manner similar to the condition which would result when one had been working in a metal shop. Using the apparatus illus trated above in Figure 3, the metal, together with some portions of loose yarn and dust, was caught on the filter paper and weighed as the sample. At first grave difficul ties were encountered in obtaining the ©ample on the round discs of filter paper, as the vacuum drew the dust parti cles off the paper and into the water system. This was overcome by placing the filter paper in the apparatus as shown. Using the paper in this manner was found to be zs thoroughly satisfactory, The sample so collected is not, of course, a pure metal sample, hut the relative percentages of the elements composing the alloy can he calculated with considerable accuracy nevertheless. In the following analysis the sample was analysed for copper, zinc, and lead, as it was known that the alloy was a hrass composed of the ahove elements. Discussion of sample. The sample used in the analysis was weighed and recorded. The analysis then pro ceeded and in eaGh ease the actual weight of the constitu ent was also recorded. These weights were then added to gether and the total so obtained was considered to he that of the total metal in the sample. Using this as a basis the realtive percentages were calculated, and the weight of the actual metal sample was placed at 0.005486 grams. Therefore the weight of the sample appears in its calculat ed form throughout this discussion, even though this weight was not obtained until all analysis was complete. Determination of lead. The weighed dust from the collector was dissolved in approximately 5 cc. of nitric acid. A clear green solution was formed, except for an abundance of fiber and yarn strands due to the cloth which the sample came. There was no precipitate formed with the 24 addition of the nitric aoid, so it was deduced that no tin was present. If ten were present, meta-stannic acid would he formed, The solution was therefore filtered to rid it of extraneous matter, The filtrate from the ahove was evaporated almost to dryness with an excess of sulphuric acid (about 8 cc.). This converted the nitrates first formed into sulphates. This sulphate residue was kept moist with sulphuric aoid, cooled, and finally 20 cc. of water were added. In this manner the sulphates formed were carried into solution by gentle heating until all but the insoluble lead sulphate disappeared. The precipitate was filtered, using the same micro funnel, with paper to fit, used throughout the rock analysis. The washed residue was then placed in a clean, weighed porcelain crucible of about 2 cc. capacity and carefully ignited. Due to the filter paper, some of the lead sulphate was reduced during ignition, so after the paper was decom posed the residue was cooled and moistened with sulphuric aoid, and reignited to constant weight. The weight so ob tained follows, the conversion factor for lead sulphate to lead being 0,6833, Wt, of sample s 0.005486 gr. Wt. of residue = 0.000156 gr. . 0.000156 x 0.6833 x__100 9 1#96 pb# Determination of copper. The copper was determined eleotrolytieally. A special type of apparatus was used for this determination. A sketch of the apparatus and its parts are included in the accompanying Figures (5 and 6). Due to the extremely small size of the cell, about 6 cc capacity, a special method of stirring was used. The anode constantly liberated gas during the procedure, so by gently heating the cell, the solution was kept in motion, both from the liberated gas and the convection currents produced by the heat. The function of the glass beads and crosses welded to the electrodes is to keep the deposited metal from being rubbed off when the electrodes are removed from the cell. For a complete discussion of this cell see footnote1. The solution from the lead filtration was evapor ated to approximately 4 cc. This solution was then trans ferred to the tube of the cell, where, together with the washings from the transfer, it approximately half filled the tube; this allows for about 6 cc. of total solution. A few drops of nitric acid were then added to depolarize the solution and prevent spongy metal deposits. The clean, dry cathode was weighed. Then with the current off, the electrodes were adjusted in the solution so that about two-thirds of the gauze electrode was submerged. The ^Emich-Schneider, Microchemical Laboratory Manuel. John Wiley and Sons, Hew York, 1932. AAfyyy/co/AA>se<7/~c^ c A / f c n * i s / > a A o s i b / ^ C t > / 0 f ? t v - sA'cAcAf (fAA3/> cA/xC o A /,/3 a t& s s r s r p A 4 c c A /A y ? ///7 /7 A /y /A c A y A c C sy/ A s' / A r/ ' / ry / 5 4 c * / rc A -o i / e s‘ / f y c y * / / f A / tz A A U ' S s ^ ' & / ir /s C c # - A v y /r c c - A o / a f t / s e j A r / s i y . / f l > / 7 c A / 7 j ' e / ' ( / < ■ v ? / b / / 7 / / 7 y u / < / A r - -g /Mercury ( * < ? / ? /frf/ / y / 7 / / s „ < 5 . /A /A /ry/Tf y z / < y y < f ( t 7 / A / * A AA/Ac’ i/y ( J / s c ’ syyjC#/ / { e - S ' A r a ’ s' S ^, 6 A / 7 j/ A . U>s/ A . c ^ / ^ / y t y s ' c / A ^ J ' A>r ^-A.r ■ / 7 7 s ' / 7 < y / £ & f £ e / ^C o yy - J^ s - {A y / A s k ST** s A A . S T f - y v / s e / y Ay?/S J/A?s/ /. / s r A s - s f c ? / A ' o ^aAf7s f ' e s ~ AA,/P. C'AcA-oc/c S?&Ac • y f /ss' j- A<?C?</i‘ b A^ At Ar A s ??<A/ i ?/ A> Ae c y c ? jv A ? /fa / \rJW-ar/PA’A &AJ e y A / A s A ^ f?A As?tsy? y y7s?acA t y s s A 4 t^A'S’ f AAarAAJ’ lAs/H i ^ A / ' y / / 0 ^ cAcsyy t? /? ^. ^A tf /r ^/ ty S/ S CeAi ! / « Vo//os»e&r &. A3 c //& a? a condenser was then put in place to prevent loss from spattering. All the resistance was put into the circuit and the current was turned on. Then by manipulation of the variable resistance an optimum reaction rate was es tablished. The current was allowed to flow until all of the copper was removed from the solution. Then with the circuit still closed, the electrodes were removed without allowing them to contact each other. ?/hile removing the electrodes from the solution they were washed with a stream of water from a small wash bottle to prevent the dissolving of the copper in the acid present. The cathode was further washed in distilled water and finally in a little acetone, and dried high above a flame. The gain in weight represented the weight of copper in the solution. Wt. of sample = 0.005486 gr. Wt. of copper s 0.003189 gr. • 0.003189 x 100 m {-q gc < s £ Co-nvveT* . . 0.005486 " 58 Determination of zinc. Addition of ammonium hy droxide to the solution from which the copper had been removed showed the absence of iron, so the determination of zinc was next in order. The solution from the electro lytic cell was exactly neutralized with ammonia, using methyl orange as an indicator. The zinc was then pre cipitated with a solution of diammonium phosphate. The acid formed during this reaction was neutralized by the 29 excess of the precipitating reagent. In this manner the solution remains buffered by the salts present and a pH of approximately 6.4-7.0 is maintained. Great care was exercised in keeping the solution under the conditions set forth above as zinc ammonium phosphate is soluble in both acid or basic solutions. Hie precipitate first obtained in the above manner was flocculent, but upon heating, this form transpired into the crystalline zinc ammonium phosphate which readily settles. The precipitate is finally filtered and washed with known quantities of cold water. The filter used was the usual micro funnel and paper. The wash water was measured so that a correction of 0.5 mg. of zinc could be made for each 100 cc. of water used. The precipitate was ignited to constant weight and weighed as zinc pyro phosphate. The following calculations were made using the conversion factor to Zn as 0.4290. Wt, of sample s 0.005486 gr. Wt. of ppt. s 0.003940 gr. 0.00394 x 0.429 5 0,001689 0.001689 plus 0.0005 (wash correction 100 cc.) * 0*003189 x 100 . *o g r f * * 0.ID05486 " S9*9 f o zino* For the purpose of checking results, the sample of brass from which the filings on the sleeve came,was most carefully analyzed by approved macro methods.2 Every effort %illard and Furman, Elementary Quantitative Analysis. Van Hostrand Co., 1933. pp 356-79. 30 was made to render this maoro analysis as aoourate as possible, and it is believed that the results here given represent very olosely the actual composition of the brass. Sable of Eesults of Metal Analysis. Element % by Macro f > by Micro Method Method head 1.73 f o 1.96 f o Copper 59.71 f o 58.35 f o 2inc 36.2 f o 39.9 ^ THE ANALYSIS OF PLASTER SAMPLES Wall plaster is of somewhat varying composition in different localities and in different houses in the same localities. It is not impossible, therefore, that plaster removed from clothing, from under finger nails, or from the hair might, in some cases, give valuable criminological evidence. It was felt that in order to analyse a given sample of plaster, determinations of the following should be made? silica, RgOg,1 calcium, magnesium, and sulfate radical. Having determined the above, much of the nature of the sample is known. The composition of plaster is so vari able that when the control sample is found to agree with the sample in question it is evidence of a common origin. Variation in the elements found in plaster is largely due to percentage of sand used in the preparation. The RgOg group, if found at all, does not vary within large limits. But the percentages of calcium and magnesium present are strong points in proof < . o f similarity. This calcium to mag nesium ratio, when it agrees, may point to an origin of the 1The term RgOg is used in analytical chemistry to denote the oxides resulting after ignition of ammonium hydroxide precipitation. The constituents present are ordinarily FegOg, AlgQg, MngO^., TiOg, and ?£0g, if phos phorus was contained in the original sample. 32 samples in the same mother mineral. The amount of sulphate present varies and is a good general similarity index. The samples were obtained from the laboratory'wall . by means of a file, and subjected to the usual pulverization in a mortar. The two samples were run side by side with no variation in either method or reagent. The micro analysis was done on the Becker micro-balance, however, while the macro determinations were done on the Chainomatic balance. About 1 gram was used for the macro analysis and 0,005 gm. for the micro analysis. The samples ?/ere first treated with appropriate quantities of hydrochloric acid and found to partially dissolve. The particles remaining were silicon compounds, largely silicon dioxide, or sand. The mixtures were then filtered, washed, and the residues ignited to constant weight. Macro sample ~ s 1.0482 gr, ,Wt. of residue s 0.5737 gr. ■ 64-75 * s*°e Micro sample “ 0.005736 gr, Wt. of residue = 0.003170 gr. ■ 0.00317 x 100 _ . $ njA . . 0,005736 " 55,4 “ 0 4 2* The determination of B.%0% group was carried out as follows: The filtrate was first treated with fitting quantities of hydrogen ohloride in order to furnish 33 sufficient ammonium ion to avoid precipitation of magnesium hydroxide upon addition of ammonium hydroxide, The solu tions were boiled for about a minute after the addition of ammonium hydroxide, the amount of which is determined by indicator changes. The precipitates so obtained were then filtered and redissolved in boiling dilute hydrochloric acid and second precipitations made. Then after washing several times with hot water the precipitates were finally ignited in porcelain crucibles. There are several wasrp=,to determine each of the constituents when necessary, but in this case the group was taken as a whole and designated RgOg constituent. It is well to say, however, that the element most prevalent in this precipitate was iron, as evidenced by the orange colored mass. The weights and percentages follow: Macro sample s 1.0482 gr. Wt, of residue = 0.0283 gr. • °*i2Q46£ 2 2.72 % % 03 group Micro sample = 0,005736 gr. Wt. of residue = 0.000121 gr. Per cent of 5 2.105. The filtrate from the above contained the calcium and magnesium portion of the sample. The filtrate is first slightly acidified with hydrochloric acid and somewhat 34 concentrated by evaporation. An amount of oxalic acid solution was added so that a ratio of one gram of plaster to 1.5 grams of the aoid was maintained. At this point a portion of the calcium precipitated, but most of it remained in solution, fo the solutions were then added a drop of methyl red as an indicator, and a solution of filtered, dilute ammonium hydroxide w$s added from a bur ette until the solutions became neutral or slightly alka line. The precipitates were then allovyed to settle for one hour, and a second precipitation was made. The mix tures were then filtered through filter papers and washed with one per cent ammonium oxalate solution. The residues were then transferred with the papers to weighed crucibles and ignited, after charring below red heat. The oxalate is first converted to the carbonate and then to the oxide. In order to obtain sufficient heat for this conversion, the crucible containing the calcium was placed above a well adjusted Meker burner on a triangle. Above this was placed a large inverted assaying crucible in which was drilled a suitable number of air holes. In this manner constant weights of calcium oxide were obtained without using platinum crucibles. The weights and percentages follow: Macro sample = 1.048E gr. Wt. of residue s Q.S401 gr. 35 0.2401 x 100 . DO 0 . , . " i happ ■ “ 22.9 p CaO, op 1.048S 16.37% Oa Mioro sample = 0.005736 gr. ft. of residue a 0,001312 gr. " ^'^on^ffi100 - 22. 8S% OaO, or . . 0.005736 16>0 £ 0a_- The filtrates from the above contained the mag nesium. To the filtrates and washings were added appro priate proportions of nitrio aoid, and the solutions evap orated to dryness. This rid the solutions of oxalate and ammonium ions, which if allowed to remain would cause the amounts of magnesium to appear high. The above ions were oxidized by the nitric and hydrochloric acid present to carbon dioxide and water, in the case of the oxalate, and to nitrous oxide and water in the case of the ammonium salts. The residues were moistened with concentrated hydrochloric acid and water. This mixture was warmed until all dis solved but a little silica resulting from the action of the various solutions on the glass, vessels. In order to rid the solutions of these particles they were filtered and washed. To the solutions’ were then added a slight excess of diammonium hydrogen phosphate dissolved in water. The liquids were then cooled in ice and while constantly stirred, concentrated filtered ammonium hydroxide was added until alkaline to' methyl red. After allowing the precipitates to settle over night, they were filtered and washed with dilute ammonium hydroxide. The precipitates were then dried and ignited in weighed porcelain crucibles under conditons similar to those of the calcium procedure. In pyrophosphate, for which the conversion factor to magnes ium is 0.21843. Macro sample = 1,0482 gr. Wt. of residue * 0.0306 gr. Determination of sulphate radical. In order to make this determination separate samples of the plaster were taken. The samples were dissolved in hydrochloric acid and the mixture filtered and washed. To this solu tion was added, with constant stirring, barium chloride solution. The solutions were tested for complete pre cipitation, allowed to settle, filtered on a filter paper, washed, and finally ignited to constant weight. The residue so obtained is barium sulphate, for which the conversion factor to sulphate radical is 0.41153. Macro sample s 0.4478 gr. Wt. of BaSO^ s 0.2066 gr. these instances the precipitates were weighed as magnesium 0.0306 x 0.218 x 100 _ 1.0482 = 0.64 f o Mg Micro sample s 0.005736 gr. Wt. of residue z 0.000166 gr. 0.000166 x 0.218 x 0,005736 s 0.63 f o Mg 37 • 0.8066 x 0.41153 x 100 , „ . . 0 4 7 8 --------- B 10.40$, sQ4 Mioro sample x . 0.004346 gr. Wt. of BaS04 = 0.001920 gr. # 0*001*20 * 0.41153 x 100 „ pn<f qn , . 0.004346 : " lO .Z O f o S04. fable of Plaster Analysis Constituent % by Macro fo by Micro Method Method Si02 54,75 fo 55,4 f R203 2.72 f 8.1 f Ga 16.37 fo 16.3 f Mg .64 f> .63% S04 18.41 f 18.20 fo Remarks. In the above analysis five variables were found to check in the control sample with the questioned one. fhe check was found to agree within limits of less than one per cent* She possibilities that two such samples taken at random would so closely check seems hardly probable. It will be noted that if the above given percent ages are added they do hot total one hundred. The macro result is 92.89 %, while the micro figure is 92,63 %, fhis discrepancy is mainly due to oarbon dioxide, which was not determined. Had time been available it could well have been spent in attempting to develop a micro method for determin ation of carbon dioxide in minerals. SUMMARY Miorochemical quantitative methods of analysis have been applied to the analysis of dust, with the idea of applying the results of the analysis to the detection of crime. An improved method for collecting dust and debris from clothing, pockets, and from almost any surface has been developed. Typical micro analyse# of mineral dust, metal, dust, and wall plaster have been made, and the results compared favorably in nearly all cases with careful analyses carried out with large samples. The necessity for more research on the micro volumet ric determination of iron has been indicated. BIBLIOGRAPHY Emich, Predrioh, Micro Chemical Laboratory Manual. John Wiley and Sons, Sew York, 193S. Scans* hyPrank Schneider* Goooh, P. A., Representative Procedures to Quantitative Chemical Analysis. John Wiley and Sons. Hew York. ifm ---------— ■ Hildebrand, W. P., and G, 1. P. Lundell, Applied Inorganic Analysis, with Speoial Reference to Analysis of Metals. Minerals, and Books. John Wiley and Sons, UeiF’ York, 19 ! ' Looard, Edmond, "Analysis of Lust Traces", The American Journal of Police Science. 1, 878 (1930). Northwestern University Press, Chicago Illinois. Looard, Edmond, Polioieos de romains. et de laboratoire. Payot, Paris, 1982. Mellor, J. W., A Treatise on Quantitative Inorganic Analysis# Griffin and”"Co., London, 1910. . Treadwell. P. P., Analytical Chemistry. Vol. II, John Wiley and Sons, Wew York, 1981. Trans, hy W* T. Hall. Washington, H, S., The Chemical Analysis of Rooks. John Wiley and Sons, Hew York, l930. Willard, H. H., and N. H. Pnrman, Elementary Quantitative Analysis. L. Van No strand Co., New York, 1933.

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Creator Bondoc, N. R (author)

Core Title Microchemical analysis of dust as an aid in the detection of crime

Degree Master of Science

Degree Program Chemistry

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag chemistry, analytical,OAI-PMH Harvest

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Permanent Link (DOI) https://doi.org/10.25549/usctheses-c17-786031

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