Barton, G. E.

English

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ARSENIC I N  GLYCEROL 883 would be increased by adding one-twentieth or one-thirtieth to the amount of titanic acid found under the conditions that we have used. T h e  great influence of the action of air is shown by two determinations which were made exactly like those given in the above table, except that, after cooling in carbon dioxide, the solutions were transferred to beakers and titrated as  quickly as  possible. Potassium titanofluoride Titanium Titanium taken Found. calculated. Error. 0.6831 0.1078 0.1366 0.0288 0.9545 0. '535 0.IgOg 0.0374 T h e  volumetric method, even without correction, will be likely to give more reliable results than those obtained by gravimetric. determination, unless great care and skill are displayed in car- rying out the latter. SHEPFIELD SCIENTIFIC SCHOOL, NEW HAVENV,  CONN. ARSENIC IN GLYCEROL. BY G. E. BARTON. Received September 9,  1895. N following up the literature of glycerol I find that the first to I note the presence of arsenic in the medicinal article was Jahns,* but he apparently did not investigate the subject thor- oughly. H e  showed the presence of arsenic in seven samples of medicinal glycerol, by the following test, which he says shows 0.001 mg. in one cc. while the Marsh test shows only 0.01 mg. in one cc. One cc. oi glycerol is placed in a small measuring cylinder and to this one cc. of water is added, together with fifteen drops of hydro- chloric acid and 0.6 gram zinc. The  top of the cylinder is cov- ered with filter-paper, moistened with a I : I silver nitrate solu- tion or saturated mercuric chloride solution, and a yellow stain is obtained on the paper if arsenic is present. Ritsert also states that ammoniacal silver nitrate solution is a good reagent for arsenious acid and that the arsenious acid present probably E. Ritsert3 was the next to take the subject up. 1 Read at the Springfield Meeting. 2 Pharni. Ztg., ,888. 652. 8 Pharm. Ztg., ,888, 715, and ~ 8 8 9 ~  1%. 360 and6q. 884 G.  E.  BARTON.  explains the difference in the indications given by litmus and phenolphthalein as observed by him. H e  gives as the probable source of the arsenic found, thesulphuric acid used in the course of manufacture. Issue is taken with G. B. Smith,’ who states that gl).cerol itself reduces silver nitrate, and hence amnionio- silver nitrate can not be used to detect arsenic. An abstract of an article by G.  ‘\‘ulpius2 gives the cost of an article free iron1 arsenic as ten per cent. more than the clirrent price. L. Siebold” on ‘ I  .Arsenic in Glycerol,” finds from one in 4000 to one in 6000 parts of arsenious acid in glycerol used for per- fuming and medicinal purposes, and in one case one part in 2500 parts. All glycerols free from arsenic were traced to oneprocess described as that “ b y  which as a rule glycerol used for dispens- ing purposes is understood to be made.” H e  ascribes the pres- ence of arsenic in some cases to the solution of the arsenic present in the glass of the bottle, but this has never been con- firmed and hardly seems probable. Dr. Henno JaffC‘ attacks the ammonio silver nitrate test which he claims to be of no value as it does not give constant results, either for arsenic or acrolein and similar bodies. J .  Luttk4,5 after an elaborate examination of twenty-one sam- ples confirms JaffC’s conclusions and points out as among the disturbing causes, chlorides and organic acids. There can be no doubt of the presence of arsenic in some gly- cerol ~ but I have found no one except Siebold who has attempted to give any idea of the quantity, and while he  does not give the method used in obtaining the results stated, I infer from the text that, using either silver nitrate or mercuric chloride to ab- sorb the hydrogen arsenide, he has compared the depth of color obtained ‘Lvith that given by known quantities of arsenious acid. A few experiments led me to think that this cannot be a very accurate method a t  best, so I set about to apply the method given by  Sanger, for the estimation of arsenic in wall paper ‘ which 1 Ned. Tijschr. v.  Pharm.. 1889, 143. 2 Apoth .  Zeit..  1889, 4, 439 ; /. SOC. Chem. Ind., 8, 639. 8 f h a r m .  J .  Tram. [3]. 20, 205. 4 Chem. Ztg. ,  z 8 p ,  14,  1493. 6 Apoth .  Z tg . ,  1891, 6, 263. 6 Proc. Amer. Acad., 26, 24. ARSENIC I N  GLYCEROL. 885 consists of comparing the mirrors obtained in a modified form of the Marsh apparatus with those prepared from known quan- tities of arsenious oxide in solution as  sodium arsenite. The  apparatus as  described by Saiiger consists of a constant hydrogen generator, filled with chemically pure sulphuric acid and zinc, a smaller reduction flask having a thistle tube for intro- ducing acid and solutions to be treated and which of course con- tains a small amount of chemically pure acid and zinc, a drying tube containing calcium chloride, and finally a reduction tube in which the mirror is obtained. The  cost of using chemically pure acid and zinc in the con- stant hydrogen generator would of course be great, and the first point I turned my attention to was a method for purifying the hydrogen generated by impure acid and zinc so that the constant generator could be run at a reasonable cost. I found that by passing the hydrogen through silver nitrate solution, the arsen- ic was removed entirely, according to the well-known reaction : ASH,+ 6AgN0,  +3H,O= H,AsO, + 6HNO,+ 3Ag,. Another improvement in the apparatus as I used it was the substitution of a small separating funnel for the thistle tube in the reduction flask. This prevented the escape of any gas a t  that point while the former arrangement allowed a variable quantity to escape. The  apparatus as finally used in this work, consisted of a con- stant hydrogen generator, using impure acid and zinc, a wash bottle containing silver nitrate solution, a wash bottle containing water to remove any traces of silver nitrate solution which the gas  might carry mechanically and which would otherwise hold back some of the arsenic in the reduction flask, a reduction flask, with separating funnel as  before described, a drying tube con- taining calcium chloride, and finally the reduction tube. The  efficiency of the silver nitrate solution was proven by running over one hundred hours without obtaining a mirror, whereas a mirror could be obtained in from five to ten minutes from the same hydrogen not passed through silver nitrate. Using the ordinary acid and zinc of the laboratory, I found an amount of silver nitrate solution representing one gram of the salt prevented the forniation of a mirror for over two hundred hours. Tlie mode of operating did not differ essentially from that  described by Sanger. Tlie apparatus was first filled with hydro- gen the reduction flask contaiiiiiig a t  this time only the pure ziiic. of jvliicli about t h e e  grams were used. The  jet at the end o i  the reduction tube \vas tlieii lit arid tlie tube heated at the  pro1)er place. after i\liicli :i little sulphuric acid was introduced i i i t (1  the reduction flask and tlit actiuxi allowed to go 011 for :L fi.\t iiiiiiutec to prove the purity of !lie reagents. T h e  solution to iw treated wis tiieii added :ind \vashed ill 1)). iiioi-e acid, or \v:iti.i- \vlic:-c. the gl>.ce.i.ol ic,.~s added tlirectl!- to the flask. ?'lie Licit1 used \vas  ximiit cnit '  to eight and l)y sliKlitl\- varying t h e x  ljroportions it \vas  found possible to get along without cooliiig tlie fl:isk. So t i vo  sanipies o i  zinc were found to con- tail1 the -3aiiie niiiouiit of carboii or at least to dissolve with the saiiic ray)itiit!- so that a careful adjustmeiit of the acid is ~ieces- graiiulatcti a t  oiie time. I t  is also iiecessar). to have  standard niirro!., iiia(le a t  tliffcreiit speetli to  couiiterbalaiice the slight cliffcreiice, ivliicli are unnvoitia1)lc. T!ie caiciuiii chloritic tube should be carefuiiy looked after in order that tlic gns may be perfectly d r y .  I have found it  best to igiiite tlic article furnished by tlie makers hefore using. I t  is also 3 g(~oti plali to attacli tlie he1lon.s and blo\v through it a few monieiitb after filling, to reiiiove any  slight :iiiioiiiit of dust that might (Jtlicrwise be carried into tlie reduction tu1w. The glas.; used for the reduction tube should he of the hardest obtaiiiable. I have found great variations i i i  different pieces of the saiiie lot. I t  would be of advantage if glass \yere carefully selected, ant1 i f  necessary carefully tested, cwuld tie quoted by dealer-,. i t 5  otherwise a large amount of tubing is accuniulated too hard for ordinary work but not hard eiiougli for this pur- pose. Great care should always he taken to get tubes uiiiform at  the point of deposition arid in spite of this it \vas found iieces- sary to have several mirrors of each grade. .I small white mirror was found to form beyond the arseiiic mirror ii i  those tubes representing sniall amounts but in those obtained from larger amounts either wholly or partly coiiiciding. In the latter case the arsenic mirror took on a totally different 4' . ai! - - t ;or each lot aiiti as large aii ainouiit a 5  possilble slioulcl be ARSENIC I N  GLYCEROL. 887 color, the chararteristic brown of the pure arsenic mirror beconi- ing black. This mirror was without doubt in some cases partly due to moisture, and showed minute drops when examined under a lens. I t  also seemed to be less with the harder glasses. After having used fresh calcium chloride and the hardest glass obtainable, the oiily resource is in having standard mirrors representing all possible variations. Another trouble .was found to be the deposition of the arsenic in two mirrors entirely apart. This  Gooch and Moseley’ sug- gest to be due to the formation of two allotropic forms of arsenic by the too high heating of the reduction tube. They avoid this by enclosing the reduction tube in an iron or nickel jacket. Here again several mirrors of each standard amount are a remedy. Having obtained a sufficient number of standard mirrors eight samples of glycerol, such as is ordinarily sold by the druggists of this city were procured. Six represented the best American makers and two were imported. Five grams of each sample were treated with five cc. of a mixture of thirty parts sulphuric acid and one part nitric acid and the mixture heated carefully with constant stirring till a dry charred mass giving off sulphur dioxide was obtained. This  was then allowed to cool and about ten cc. of water added and then the mass again heated till sulphur dioxide was given off. After cooling about fifteen cc. of water was added and the mixture boiled vigorously to expel sulphur dioxide. The  liquid was then filtered off and water added as  before, boiled and again filtered. This  was repeated twice to insure the complete extraction of the arsenic from the charred mass. The  solution thus obtained was added to the reduction flask and the usual process carried out. Five of the eight samples showed arsenic in variable amounts. To prove that arsenic, if present, would be shown by this course of manipulation, five grams of glycerol showing no arsenic were weighed out and one cc. of an arsenic solution added. This  mixture was treated exactly as  the other samples had been and no arsenic mirror obtained. From this and the comparison 1 Am. J. Sci., 48, 2%. of these iiiirrors with those obtained b y  other processes. I con- cluded that some, a t  least of tlie samples contain, or are deconi- posed into something capable o! holding black arsenic. This  leads to tlie query : \I'liat is the effect of the combined glycerol present in the toxicological exaiiiinatioii for arsenic ? Ma!. not the trouble with the gl;:cerol be due to a decomposition product wliicli would also be formed in the snpposed case ? I have not had time to investigate this iiiiportant point. Five grams of tlie sameglycerol used in the previous experiment were then added direct to the reduction flask after clilutiiig with water and arsenic in siiiall quantities was obtained. One c c .  of the arsenic solution was then added to tlie glycerol ant i .  after diluting, the reduction carried out at once as iri the previous experiment and an amount of arsenic equal to that i n  the one cc. of solution and five grnnis of glycerol, obtained. After trying se\.cral plnns this iiietliod was filially chosen as both the quickest and most accurate. The followiiig quantities of arsenious oxide ( As20:,~) were obtained in the eight saniples : SI>. h.0. 1 . . . . . . . . . . . . . . . .  trace. 5 . . . . . . . . . . . . . . . .  f ; i i i ~ t  race. . . . . . .  0.08 ing. 6 . . . . . . . . . . . . . . . .  trace. faint  trace,  7 . . .  . . . . . .  (J .004 lflg. none. 8 . . . . . . . . . . . . . . . .  0.003 nig. To  prove that the niirrors obtained were due to arsenic and nothing else, mirrors were heated gent1)- and nioist hydrogen sulphide passed through them. In  this niaiirier part of the arsenic was changed to the yellow sulphide. Some of the gas  from the reductioii flask was passed into silver nitrate Solution arid a black precipitate of metallic silver obtained. On carefully neutralizing with ai i~~noniuni  hydroxide a yellow precipitate of silver arsenite, soluble in excess, and also in nitric acid was ob- tained. The  nitric acid solution was precipitated with hydro- chloric acid, a clean copper wire added and the solution warmed. A grey coating formed on the copper. Blank experiinents showed the reagents to be pure. From the above there can be no doubt but that arsenic was present in the glycerols examined. The  inetliod iiientioned by several authors, naniely, diluting ARSENIC IN GLYCEROL. 889 the glycerol with an equal volume of water, adding hydrochloric acid and then metallic zinc, and obtaining a yellow coloration on a filter-paper moistened with either silver nitrate solution ( I  : I )  or saturated mercuric chloride solution was tried. A twenty-five cc. measuring cylinder was used and the paper fastened tightly over the mouth, the gas escaping a t  the nose. I n  this maqner using the silver nitrate solution the test was found to be about five times as delicate as the Marsh test used, and a trace of arsenic was found in sample No. 4, which had shown none in the Marsh test. The  coloration was not permanent enough, owing to the action of light and other causes to be compared with standards made with permanent coloring-matters. The  test with mercuric chloride, carried out in the same way, was not quite as  delicate as  the Marsh test. I t  would hardly be possible by comparing with standards to make this a quantitative method as  accurate as the Sanger-Berzelius-Marsh test. It is to be noted that sample No. 2, which showed the largest amount, contained 0.08 arsenious oxide or one part in 6 2 5 0 0 ,  while Siebdld reports as much as one part in 2 5 0 0  in oqe case. Seventy nig. is the smallest dose known to have produced death according to Tan-  ner’ which would be equivalent to the amount in over four liters of glycerol No. 2, or to 150 cc. of Siebold’s worst sample. Although arsenic is slowly eliminated from the system, still it would be quite possible by the indiscriminate use of sample No. 2, for some time, to accumulate enough in the system to cause death. Certainly the above figures are worthy of note by persons using glycerol for medicinal purposes. So-called C. P. glycerol is often recovered from the waste products of the soap manufactories, and in this case the presence of arsenic is accounted for as follows : Starting with arsenical oil of vitriol, the arsenic is changed in the hydrochloric acid still to the chloride, which distils over with the acid. On neutraliz- ing the spent lyes with hydrochloric acid the arsenic remains in the solution and is repeatedly distilled over with the glycerol. In this connection I may say that I found no hydrochloric acid in this laboratory free from arsenic as shown by the yellow stain in the silver nitrate test, but had no trouble in preparing such 1 Memoranda of Poisons, p.  69. 890 T R I M E T H Y L E N E  GLYCOL AS A BY-PRODUCT. an article from chemically pure sulphuric acid which I had proven to contain no arsenic. In  conclusion I take pleasure in acknowledgirig my deep in- debtedness to Dr. Charles E.  Munroe for his many suggestions. T H E  COLCMBIAK r K I V E R S I T \ - .  WASHIKGTON,  D. C. T H E  OCCURRENCE OF TRlf lETHYLENE GLYCOL A S  A BY-PRODUCT IN T H E  GLYCEROL MANU- FACTURE.' BY A R T H U R  A .  N O S E S  A S D  W I L L A R D  H. W I T K I X S .  Ilcce1ved Se,>tv :nLM 8 ,  >89j. URING the past winter our attention was called to an D unusual difficulty experienced by one of the soap-making firms in the neighborhood of Boston i n  obtaining their glycerol of the required commercial gravity. The  inforination furnished in iegard to it indicated the presence in the glycerol of some uncommon impurity, and a considerable quantity of the I '  light stuff" having been generously placed at our disposal by the soap companj., we were enabled to investigate it. I t  was sub- mitted to fractional distillation, first at diminished and then at ordinary pressure, and a liquid boiling between 214' and 217' at 760 mill. pressure was thus separated from it. This liquid was found to have a specific gra\?ity of 1 .o j6  at 3$-, and gave the following resu!ts on analysis : 0.2293 gram substance gave 0.3998 gram carbon dioxide and 0 . 2  158 gram water. 1;oulld. Calciilated for CIH,Og. ................... Carbon 47.52  47.37 Hydrogen 10.46 70..53 The substance is therefore trimethylene glycol, which has a boiling-point of 214' and a specific gravity at '$-' of 1.0526. The  isomeric propylene glycol boils a t  188"-18g" and has a specific gravity of 1.0403 at Lg:?. The "light stuff'' contained a very considerable proportion, about thirty-eight per cent. of The  origin of the glycol is a matter of considerable interest. There is little doubt that it was produced by fermentation of the ................ glycol. 1 Read at the springfield meeting 

Arsenic in Glycerol. 1

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Arsenic in Glycerol. 1

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