ARSENOMOLYBDIC AGIU AS AN 
 ALKALOIDAL REAGENT 
 
 HY 
 
 GEORGE SEARLES SPILVER 
 
 THESIS 
 
 FOR THE 
 
 DEGREE OF BACHELOR OF SCIENCE 
 
 IN 
 
 LIBERAL ARTS AND SCIENCES 
 
 COLLEGE OF LIBERAL ARTS AND SCIENCES 
 
 UNIVERSITY OF ILLINOIS 
 
 1922 
 
Digitized by the Internet Archive 
 in 2015 
 
 https://archive.org/details/arsenomolybdicacOOspil 
 
UNIVERSITY OF ILLINOIS 
 
 ..ig3.2... 
 
 THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION BY 
 
 GE0RGF..SMRLES...5PTLYKB 
 
 ENTITLED ARSE NOMO L.YBDI C . . A C J D . . A. § . .AIL .AM A LQ.I.P.A L. . . REAGO.T 
 
 IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE 
 DEGREE OF BACHELOROF SCIENCE. JN..MBEHA.I-....A.RTS.. AU.D...SC.IM.CES 
 
 Approved 
 
 HEAD OF DEPARTMENT OF pH^ISTRY 
 

 
 
 
 
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Acknowledgment 
 
 The writer desires to take this opportunity 
 to express his appreciation of the help and guidance given by 
 Dr. G.D. Beal in the preparation of this thesis. 
 

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Index 
 
 Page 
 
 I. Introduction 1 
 
 II. Preparation 2 
 
 III. Analysis and Calculations 3 
 
 IV. Arseno-molybdic Acid as a Qualitative 
 
 Reagent for Alkaloids 10. 
 
 V. Conclusion 12 
 
 VI . Bibliography 13 
 

 
 
 
 
 
 
 
 
1 
 
 Arsenomolybdic Acid as an 
 Alkaloidal Reagent 
 
 I 
 
 Intrcduct ion 
 
 It has been the purpose of this work to prepare arsenomoly- 
 bic acid, to determine its formula, and to investigate its value 
 as an alkaloidal precipitant. 
 
 V/ork on arsenomolybdic acid as an alkaloidal reagent is not 
 found in the literature to date. However, Seybertfcr’ gives the 
 preparation and some reactions of an ammonium salt of arsenomoly- 
 bic acid. Freidheim^ also gives the analysis of salts prepar- 
 ed by the action of molybdic anhydride on ammonium arsenate and 
 of ammonium molybdate on ammonium arsenate. 
 
 In this work the method of treating an acid solution of 
 ammonium molybdate with arsenic acid, and also by salting out 
 from this solution with ammonium salt was used in the preparation. 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
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2 
 
 II 
 
 Preparation 
 
 One hundred grains of molybdic acid were dissolved in 50C 
 cc of 2.5/n ammonia. This solution was then very slowly added 
 with constant stirring, to 1000 cc of 6.3/n nitric acid, the 
 temperature of the mixture being maintained at zero degrees 
 centigrade throughout the addition. A soultion of forty 
 grams of sodium arsenate slightly acidified with nitric acid 
 was then added, and the mixture was heated on a water bath 
 at from 50 to 60 degrees centigrade. Heating continued at 
 this temperature for 24 hours produced about 25 grams of fine 
 light yellow, crystalline precipitate which was then filtered 
 of f . 
 
 The addition of 300 grams of ammonium nitrate, which with 
 the 50 grams ( approximately) resulting from the previous neu- 
 tralization, made a total of 350 grams in the two liters of 
 solution, caused the precipitation in the course of 8 hours at 
 the same temperature of some 50 grams of cyrstals. This yield 
 was of a slightly darker yellow than that obtained previously. 
 The further addition of 100 grams of ammonium nitrate and con- 
 tinued heating ysilded now about 20 grams of precipitate after 
 8 hours. After standing several days about 10 grams more 
 

 
 
 
 
 
 
 
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3 . 
 
 precipitate was filtered from this same solution. 
 
 Still two more filtrations were made of this solution 
 after it had stood in each case about one week at room tem- 
 perature, and each time about 1C grams were obtained. The 
 six yields varied in color from a light yellow ( first) to 
 a somewhat brighter yellow( last sample). However, the vari- 
 ation in shade being greatest between samples one and two. 
 
 It will be recalled that sample one was obtained before salt- 
 ing out. These samples obtained by the several filtrations 
 were kept in separate containers in order that separate analy- 
 sis of them would be possible. 
 
 In the course of the procedure it was noted that if the 
 acid mixture from which the yellow crystals were precipitated, 
 was slowly neutralized with ammonia, the molybdic acid would 
 be precipitated instead of the desired product. 
 
 Ill 
 
 Analysis 
 
 The product, after drying was examined under the micro- 
 scope and found to appear homogeneous, altho the several sam — 
 pies differed somewhat in size of the crystals. 
 
 The following qualitative tests were made: the precipita- 
 tion of magnesium ammonium arsenate by magnesia mixture indicat 
 

 
 
 
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4 . 
 
 ed the presence of arsenic; warming the substance with sodium 
 hydroxide and testing the vapor with wet litmus paper indicated 
 the presence of the ammonium radical; reduction to various shades 
 of blue or blue green indicated the presence of molybdenum, 
 
 A quantitative analysis for these substances was conduct- 
 ed as follows: 
 
 1. Determination of Arsenic content. Half gram samples 
 of the ammonium arsenomolybdate were dissolved each in 100 cc . of 
 water, treated with 5 cc . of concentrated hydrochloric acid. 
 Twenty-five cc. of magnesia mixture was added, and after neutral- 
 ization with 10$ ammonium hydroxide, an excess of l/3 the volume 
 of the neutralized solution was added. After standing 24 hours 
 the solution was filtered through a Gooch ( asbestos) crucible, 
 the precipitate was washed with 2.5$ ammonium hydroxide, and 
 dried at 100° centigrade. The precipitate was then ignited 
 in a muffle furnace up to 900° centigrade, cooled, and weighed 
 as magnesium py roar senate ( Ugg As 3 Oy ) 
 
 Sample 
 
 $ As 
 
 Sample 
 
 $ As 
 
 1 
 
 13.74 
 
 4 
 
 — — 
 
 
 13.08 
 
 
 6.19 
 
 2 
 
 6 . 85 
 
 5 
 
 6.22 
 
 
 7.31 
 
 
 6.39 
 
 3 
 
 6.78 
 
 6 
 
 5.68 
 
 
 7.42 
 
 
 5.33 
 
 . Determination of 
 
 ammonium 
 
 content , 
 
 
 One third gram samples were dissolved in 200 cc . of water 
 and distilled with 25 cc. of 5$ (wt) sodium hydroxide solution 
 

 
 
 
 
 
 
 
 
 
 
 
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 iJw* I 1 1 1 1 I 
 
 
 
 
5 * 
 
 previously boiled. Distillation was continued until the distil- 
 late was 2/3 the volume of the original solution. The distillate 
 was received in 25 cc. of n/lO solution of hydrochloric acid and 
 the excess titrated with standard sodium hydroxide. 
 
 Sample $ NH^ 
 
 1 2.4 
 
 2.5 
 
 2 4.6 
 
 4.7 
 
 3 5.1 
 
 4.2 
 
 4 4.3 
 
 5.0 
 
 3. Determination of molybdenum content. 
 
 The alkaline filtrates from the arsenic precipitations 
 were used for the molybdenum determinations. After most of 
 the free ammonia had been removed by heating, the filtrate was 
 neutralized with dilute sulfuric acid and evaporated to about 
 100 cc. Ten cc. of dilute sulfuric acid was added and the so- 
 lution placed in a 300 cc. oval pressure flask which had a por- 
 celain top like that of a citrate of magnesia bottle. After 
 the air in the flask ?<ras partly removed by the application of 
 vacuum, the flask was connected with hydrogen sulfide under pres- 
 sure until the solution was saturated with the gas. The stopper 
 was then fastened and the flask placed in a water bath at a 
 temperature of from 60 to 80 degrees centigrade for about half 
 
6 . 
 
 an hour . 
 
 Filtration through an asbestos Gooch crucible proved in- 
 adequate as the molybdenum sulfide was partly in the colloidal 
 state. This difficulty was overcome by heating the solution for 
 a longer period at a slightly higher temperature ( 80 to IOC 
 degrees for about an hour and allowing to stand over night). It 
 was found that from three to five successive precipitations were 
 necessary for the complete removal of the molybdenum from the 
 solution. Incomplete removal was evident in any case by the 
 blue color of the filtrate. 
 
 Another difficulty was now encountered in that some of the 
 sulfide in the crucible was oxidized by the air, in the interval 
 between filtrations, to soluble compounds which were washed 
 through into the filtrate at the following filtration. It was 
 realized that a quantitative separation by this method would be 
 impossible without more elaborate equipment, either in the way 
 of a reducing atmosphere for the precipitate, or the employment 
 of fresh Gooch crucibles for each filtration. Thinking this 
 inadvisable, the writer decided to employ a different method, 
 namely; of filtering each time through a fresh quantitative fil- 
 ter paper. 
 
 After drying the filter, the brownish-black precipitate was 
 removed as well as possible and preserved between watch glasses 
 while the filter paper was burned in a weighed crucible. The 
 precipitate was then added to the crucible and ignition to the 
 oxide attempted. This step in the process proved unsatisfactory. 
 The sulfide was found very prone to deflagrate and the molybdic 
 

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7. 
 
 3 
 
 acid to volitalize as stated by Mellor . A number of the 
 precipitates were ignited and in each case it proved difficult 
 to maintain the proper temperature, for with too small a flame 
 the ignition was exceedingly slow, and with a slightly larger 
 flame deflagration took place unexpectedly from time to time. 
 Moreover, after this stage was passed it was difficult to com- 
 pletely convert the blue residue to the white oxide without caus- 
 ing some volatization. 
 
 A third method was now tried. It was intended to ignite 
 
 the precipitate with a little pure sulfur in a current of ir/dro- 
 
 4 
 
 gen by means of a Rose crucible . Consequently a Kipp 
 
 hydrogen generator was set up and to which was connected, a 
 wash tower containing potassium permanganate in concentrated 
 sulfuric acid, a wash tower containing 40 per cent sodium hydrox- 
 ide solution, and also a calcium chloride drying tower. However, 
 at this time it was found impossible to get complete precipita- 
 tion of the molybdenum, sulfide, as previously. It was attempt- 
 ed with solutions of sulfuric acid content ranging from 5 to 
 60 cc of the dilute acid in 150 cc. of solution, but in each 
 
 case the blue color of the filtrate persisted. 
 
 5 
 
 A fourth method was now tried. The arsenic was first 
 removed as before by precipitation with magnesia mixture. The 
 excess ammonia was neutralized with hydrochloric acid. A few 
 drops of ammonium hydroxide were added and then 2 or 3 cc. of 
 acetic acid ( 33 per cent) in excess and the solution diluted 
 to 200 cc . The solution was boiled. Boiling was continued 
 while 40 to 50 cc . of a lead acetate solution ( 40 grams of 
 
8 . 
 
 lead acetate crystals per liter) were added and then for four 
 more minutes accompanied with vigorous stirring. The precipi- 
 tate was allowed to settle, and then was filtered thru asbestos 
 in a Gooch crucible with suction. The precipitate was washed by 
 decantation with a boiling solution of 25 grams of ammonium chlor- 
 ide and ten drops of acetic acid per liter until free from lead. 
 The washings were tested with hydrogen sulfide for lead. 
 
 In washing by decantation, the wash solution was kept a 3 
 hot as possible and the mixture stirred vigorously before each 
 decantation. After being washed free from lead, the precipitate 
 was washed twice with boiling water. The crucible was heated 
 on an asbestos plate until dry and then over a free flame. It 
 was cooled and the precipitate weighed as ?b Mo O 4 . 
 
 Sample 
 
 1 
 
 2 
 
 47.29 
 
 48.36 
 
 3 
 
 49.42 
 
 48.21 
 
 4 
 
 51.17 
 
 51.34 
 
 5 
 
 46.16 
 
 46.10 
 
 4. Determination of moisture content 
 
 For this determination samples were heated in an electric 
 
 oven 
 

 
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 IlflH 
 
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Sample /&loss at 
 
 100°C 
 
 9s 
 
 $ loss at 110°C <fo loss at 150°C 
 
 1 
 
 1.27 
 
 
 1.77 
 
 2.38 
 
 2 
 
 4.06 
 
 
 5.21 
 
 6 .06 
 
 3 
 
 2.87 
 
 
 3.70 
 
 4.53 
 
 4 
 
 1.68 
 
 
 2.33 
 
 3.30 
 
 
 Calculations 
 
 The following calculations were made from the 
 
 data obtain- 
 
 e& by 
 
 the analyses in order 
 
 to determine formulae, 
 
 if possible: 
 
 
 ( Percentages figured on samples as obtained) 
 
 foMo 
 
 folloOZ 
 
 $ As 
 
 i° as 2 0 S $ hh 4 
 
 Total $ 
 
 47.34 
 
 71.01 
 
 13.08 
 
 20.05 2.5 
 
 93.56 
 
 47.29 
 
 70.93 
 
 6.85 
 
 10.50 4.6 
 
 86.03 
 
 48.36 
 
 72.54 
 
 7.31 
 
 11.21 4.7 
 
 88.45 
 
 49.42 
 
 74.13 
 
 6.78 
 
 10.39 5.1 
 
 89.62 
 
 48.21 
 
 72.31 
 
 7.42 
 
 11.38 4.2 
 
 89.89 
 
 51.17 
 
 76.75 
 
 — 
 
 4.3 
 
 — 
 
 51.34 
 
 77.01 
 
 6.19 
 
 9.49 5.0 
 
 91.50 
 
 46.16 
 
 69.24 
 
 6.22 
 
 9.54 
 
 — 
 
 46.10 
 
 69.15 
 
 6.39 
 
 9.80 
 
 — 
 
 ^MoC '3 
 
 r- 144 /iASgOg-i- 
 
 230 
 
 Peat io 
 
 $NH 4 * 18 M0O3 As 2 0 5 
 
 nh 4 
 
 .4931 
 
 .0871 
 
 
 .1389 5.66 1 
 
 1.59 
 
 .4926 
 
 .0456 
 
 
 .2556 10.80 1 
 
 5.60 
 
 .5038 
 
 .0487 
 
 
 .2611 10.34 1 
 
 5.36 
 
 .5148 
 
 .0451 
 
 
 .2833 11.42 1 
 
 6.28 
 
 .5022 
 
 .0494 
 
 
 .2333 10.17 1 
 
 4.72 
 
 .5348 
 
 .0412 
 
 
 .2778 12.93 1 
 
 6.74 
 

10 .. 
 
 #Mo 
 
 ( Percentages 
 $Mo 0 3 joke 
 
 figures on 
 jo A s 2 0 5 
 
 samples dried at 
 f»KH 4 
 
 110°C) 
 
 Total 
 
 48.19 
 
 73.28 13.32 
 
 20.42 
 
 2 .54 
 
 95.24 
 
 49.89 
 
 74.83 7.22 
 
 11.07 
 
 4.85 
 
 90.75 
 
 51.03 
 
 76.53 7.71 
 
 11.82 
 
 4.95 
 
 93.30 
 
 51.32 
 
 76.98 7.04 
 
 10.79 
 
 5.29 
 
 93.06 
 
 56.06 
 
 75.09 7.70 
 
 11.80 
 
 4.36 
 
 81.2 5 
 
 53.39 
 
 78.59 
 
 — 
 
 — 
 
 — 
 
 52.57 
 
 78.85 6.33 
 
 9.70 
 
 5.11 
 
 93.66 
 
 ybMoO^ t 
 
 144 foAsgOg * 230 
 
 $1TH 4 -r 18 
 
 Ratio 
 
 MoOg AsgOg 
 
 nh 4 
 
 .5030 
 
 .088.7 
 
 .1411 
 
 5.65 1 
 
 1.58 
 
 .5197 
 
 .0481 
 
 .3694 
 
 10.80 1 
 
 5.58 
 
 .5315 
 
 .0514 
 
 .2750 
 
 10.34 1 
 
 5.35 
 
 .5346 
 
 .0409 
 
 .2939 
 
 11.39 1 
 
 6.26 
 
 .5215 
 
 .0513 
 
 .2422 
 
 10.16 1 
 
 4.72 
 
 .5476 
 
 .0421 
 
 .2839 
 
 13.98 1 
 
 6.70 
 
 IV 
 
 Arseno-LIolybdic Acid as a Qualitative Reagent For 
 
 
 Alkaloids . 
 
 Solutions of the alkaloids quinidine, cinchonine and 
 cinchonidine in hydrochloric acid were prepared and to each was 
 added arsenomolybdic acid solution ( a solution of the ammonium 
 salt in dilute hydrochloric acid) until the precipitation was 
 complete, and then an excess added. The treatment of the clear 
 filtrate with Mayer's reagent gave no precipitate or cloudiness 
 

 
 
 
 
 I 
 
 
 
 
 
 
11 
 
 to the solution. 
 
 Samples of salts prepared in this work were heated over 
 a wide range of temperature, starting at one hundred degrees 
 centigrade. Color changes, were observed, which, altho not 
 bearing directly on the subject of this work, were quite interest- 
 ing. The writer has attempted to describe these color changes in 
 tabular form, and the temperature given are approximate. 
 
 Sample 
 
 100° 
 
 105° 
 
 lighter 
 
 125° 
 
 185° 
 
 white to 
 
 190° 
 
 1 
 
 yellow 
 
 yellow 
 
 dark 
 
 wh it e 
 pale 
 
 pale green 
 
 pale green 
 
 2 
 
 ii 
 
 yellow 
 
 yellow 
 
 orange 
 
 " yellow 
 
 " orange 
 
 3 
 
 it 
 
 it 
 
 yellow 
 
 orange 
 
 deep orange 
 
 4 
 
 ti 
 
 it 
 
 ii 
 
 n 
 
 deep orange 
 
 
 210° 
 
 230° 
 
 250° 
 
 2 70° 
 
 
 
 pale green 
 
 
 dark green 
 
 1 
 
 pale green 
 
 to brown 
 
 green brown 
 
 to brown 
 
 2 
 
 orange to 
 green 
 
 orange 
 
 green 
 
 and 
 
 myrtle green 
 
 myrtle green 
 
 
 orange to 
 
 orange 
 
 and 
 
 myrtle green 
 
 myrtle green 
 
 3 
 
 green 
 
 green 
 
 
 
 
 
 
 orange 
 
 and 
 
 dark orange 
 
 dark orange 
 
 4 
 
 orange 
 
 green 
 
 
 and green 
 
 and green 
 
 
 300° 
 
 
 asbest 1 
 
 os gauze 
 
 
 
 
 3 in. 
 
 flame 
 
 4 in. flame 
 
 1 
 
 shiny brown 
 
 
 deep green ) 
 
 shinny brown 
 
 
 
 
 
 )all 
 
 
 2 
 
 green brown 
 
 
 yellow 
 
 green) smoke 
 
 dark green 
 
 
 
 
 
 )and 
 
 3 
 
 green brown 
 
 
 yellow green) give 
 
 dark green 
 
 
 
 
 
 ) of f 
 
 
 4 
 
 green brown 
 
 
 orange 
 
 green; fumes 
 
 dark green 
 
* 
 
 
 
 
 
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 * 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
12 
 
 Sample 
 
 5 
 
 in. flame 
 
 red heat 
 
 when 
 
 . cool 
 
 
 1 
 
 dark 
 
 blue green 
 
 orange yellow 
 
 shinny 
 
 silver 
 
 fthite 
 
 2 
 
 moss 
 
 green to blue 
 
 yellow 
 
 sh inny 
 
 silver 
 
 white 
 
 3 
 
 moss 
 
 green to blue 
 
 yellow 
 
 shinny 
 
 silver 
 
 white 
 
 4 
 
 moss 
 
 green to blue 
 
 yellow 
 
 sh inny 
 
 silver 
 
 white 
 
 V 
 
 Conclusions 
 
 It is believed that from the results of this work the 
 following conclusions may be drawn; 
 
 1. That the ammonium salt of an arsenornolybdic acid was 
 prepared . 
 
 2. That by treating ammonium molybdate in acid solution 
 with sodium arsenate one complex was formed, while by salting 
 out from the same solution a different complex was formed. 
 
 3. That of the samples prepared the first has probably 
 one formula and the others another formula. The samples pre- 
 pared were not purified and consequantly from the data obtained 
 by the analyses it is not possible to conclude definite formulae. 
 
 4. That the arsenornolybdic acids prepared, or their salts 
 in acid solution, are quantitative precipitants for alkaloids. 
 

 
 
 
 
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