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of acetylsalicylic acid examined, all of them with one exception (acetylsalicylic acid, Millikin, j-grain capsules, purchased on the open market) complying with the tests described in this paper. T h e J o w n a l of the America% Medical Association, in past years, has protested repeatedly against the monopoly given t o the Bayer Company for their “Aspirin,” contending t h a t acetylsalicylic acid (aspirin) was not new, and t h a t “Aspirin, Bayer” was simply a good brand of acetylsalicylic acid which could be bought in foreign countries a t much lower prices t h a n here. Although t h e patent in the United States has expired, “Aspirin, Bayer” is still being retailed a t higher prices t h a n other products which are now enjoying the privilege of American manufacture. Mr. Paul Bakewell,’ in a n opinion answering the warning circular of t h e Bayer Co. in reference t o the use of the w-ord “aspirin” by firms other t h a n Bayer, argues very ably t h a t acetylsalicylic acid, before the patent was granted, meant the impure substance which was not used therapeutically, while “aspirin” was designated as the improved product (a new article of manufacture, the particular acetylsalicylic acid made under the Hoffman patent) and “is the substance now known in pharmacy as aspirin” (statement made by an officer of the Farbenfabriken of Elberfeld Co. in U. S. Circuit Court, 1909). The products reported in this paper are (with the one exception) the same as described in the Hoffman patent, and, in the sense of Mr. Bakewell’s argument, are “aspirin.” However, i t would seem better if the name acetylsalicylic acid, instead of aspirin, were used, especially by physicians in their prescriptions because (I) it is a generic, scientific name; ( 2 ) “Aspirin, Bayer” is sold a t higher prices t h a n other products, whereas chemically equivalent products sold under the descriptive name may be purchased a t a lower price. Finally, the manufacture of acetylsalicylic acid in this country is another example of the fact t h a t American chemists can produce the drug synthetics, and a t the same time make products as good as, if not better than, those of German origin. I express my appreciation t o Dr. W. A . Puckner for his kind interest.
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titrated with sodium thiosulfate in the usual manner. I t is not proposed t o discuss in detail the various modifications of these methods t h a t have been suggested and investigated in connection with the analysis of arsenical insecticides. The reader is referred t o the exhaustive reports published in the Journal of the Association of O f i c i a l Agricultural Chemists, 19I 5 , 1916 and 1917. The method adopted as official b y the A. 0. A. C. for the determination of total arsenic is based upon the distillation of the arsenic as arsenious chloride by means of cuprous chloride and concentrated hydrochloric acid. The distillate obtained is diluted t o a definite volume and aliquot portions are titrated with iodine in t h e presence of sodium bicarbonate.’ The object of this paper is t o show that the iodate titration as applied t o t h e determination of arsenic has many advantages over t h e iodimetric methods. The iodate method, which is based upon titrating arsenious compounds with a standard solution of potassium iodate in the presence of 1 1 t o 20 per cent of hydrochloric acid, until the iodine liberated during the first part of the reaction has disappeared from the chloroform indicator, was first described by L. W. Andrews.2 More recently the writer3 has shown t h a t arsenic can be accurately determined by this method, and confirmed the results obtained by Andrews. It may be well t o enumerate again the advantages of the iodate titration over the iodimetric for those who are not familiar with t h e literature on this subject. One great advantage is t h a t the iodate solution is prepared ready for use by simply weighing the calculated amount of pure dry normal potassium iodate: dissolving i t in water, and diluting to the proper volume. No further standardization of this solution is required a t any time so long as the evaporation of the water is prevented (a solution kept for seven years showed no measurable change). This is in marked contrast t o the work and time required t o prepare the iodine solution as well as the sodium arsenite or sodium thiosulfate solutions used for its standardization and the restandardization necessary a t frequent intervals. Another marked advantage in favor of the iodate titration is the exceedingly sharp and definite end-point obtained with the chloroform indicator, Furthermore cupric and ferric compounds as well as most kinds of CHEMICAL LABORATORY AMERICAN MEDICALASSOCIATION organic matter have no influence upon the accuracy CHICAQO, ILLINOIS of the method. I n t h e direct titration of insecticides, cuprous and antimonious compounds react with THE DETERMINATION OF ARSENIC IN INSECTICIDES2 potassium iodate as is the case with the iodine titration, but fortunately these compounds occur only in BY POTASSIUM IODATE very small amounts. B y GEORQES. JAMISSON Received January 8. 1918 I n connection with the determination of total arsenic The methods employed for the determination of in which the distillation process is employed in order arsenic in insecticides are based upon the well-known t o obtain all the arsenic in the trivalent condition, iodimetric processes. Arsenious compounds are the iodate titration has the advantage over t h e iodine titrated with iodine in the presence of a n excess of method not only in regard t o the time required but sodium bicarbonate. Arsenic compounds in a strongly also in t h a t no sodium hydroxide or sodium bicarbonate acidified solution are treated with potassium iodide is used. The first potassium iodate solution employed and the iodine which is liberated by the reaction is in the present investigation contained 3.567 g. of 1 “In the Matter of Aspirin. Answer to the warning circular of the Bayer Co. of June 1, 1917,” by Mr Paul Bakewell, Monsanto Chemical
Works.
* Published b y permission of the Secretary of Agriculture.
Roark and McDonnell, THIS JOURNAL, 8 (19161, 327. J. Am. Chem. SOC.,26 (1903), 756. 3 THISJOURNAL, 3 (1911), 250; A m . J . Scz., 44 (19171, 150. 4 I b z d , 44 (1917). 151. 1
2
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KI03 in 1000 cc. It had the value I cc. = 0.003300 g. of As& When this solution was exhausted, a more convenient one was prepared. I t contained 3.244 g, of K I 0 3 in 1000 cc. and had the value I cc. = 0.003000 g. of As203. For t h e preparation of these solutions, Kahlbaum's pure normal potassium iodate which had been dried a t 140' C. was used. The reaction between the potassium iodate and arsenious compounds is represented by the following equation: AS203
+ KI03 + ZHCl = As205 + IC1 + KC1 + H2O'
For the determination of arsenious oxide in Paris green or other arsenite from 0.15 t o 0.4 g. of the sample, depending upon the amount of arsenic present, was weighed directly into a 2 5 0 cc. or 500 cc. glass-stoppered bottle. 30 cc. of hydrochloric acid, sp. gr. 1.19, 2 0 cc. of water, and 6 cc. of chloroform were added. The titration was made by adding the potassium iodate solution, rapidly a t first, while shaking the bottle so as t o give the contents a gyratory motion. When the iodine which is liberated during t h e first part of the titration has largely disappeared from the solution, the stopper is inserted and the contents of the bottle are given a thorough shaking. From this point, the titration is continued cautiously, shaking the stoppered bottle after each addition of iodate solution, until the iodine color of the chloroform has disappeared which marks the end-point. It is customary t o allow the titrated solution t o stand 5 min., then if, after shaking again, any color is observed in the chloroform, it is expelled with the smallest possible amount of iodate solution. It is very important t o shake the solution more thoroughly the nearer the end-point is approached, otherwise t h e solution may be over-titrated. Furthermore, i t has been found t h a t the larger the volume of the solution being titrated, the more shaking is required t o bring the chloroform carrying the iodine in contact with the potassium iodate. The entire determination, after a little practice with the iodate titration, can usually be completed in about 1 5 min. It should be observed t h a t as Andrews2 has shown, the strength of the hydrochloric acid in which the titration is made, is of much importance. The acidity of the solution a t the end of the titration should not be less t h a n 1 1 per cent of actual hydrochloric acid so as t o prevent the hydrolysis of the iodine monochloride. On the other hand, the acidity should not be over 2 0 per cent, otherwise the reaction proceeds very slowly. I t is a simple matter t o keep the acid within the required limits. I n order t o facilitate calculations, and also if it is desired t o weigh larger amounts of the insecticide, a gram or factor weight may be employed. I n such cases i t would be recommended t h a t the sample be dissolved in 2 0 0 cc. of hydrochloric acid, sp. gr. 1.19, and made t o 5 0 0 cc. volume; then t o each I O O cc. aliquot, I O cc. of hydrochloric acid should be added t o maintain the proper acidity. Using a potassium iodate solution of which I cc. = 0.0033oo g. Asz08, the following results were obtained : 1
A m . J . Sci., 44 (19171,151.
2
L O G . cit.
291
PERC ENTAGE AszOs FOUND c c . of Hedge's Gram KIOa Iodate Modified INSECTICIDE Taken Used Method Method Paris Green No. 12542 0.1287 22.2 56.92 57.05 Paris Green No. 12542.. 0.1166 20.1 56.88 56.93 Paris Green No. 12542.. 0.1207 20.8 56.87 Paris Green No. 12542.. 0.1325 22.85 56.90 Paris Green No. 12489.. 0.1794 33.92(c) 56.72 si:is Paris Green No. 12489.. 0.1533 28.95(c) 56.65 Paris Green No. 12489.. 0.1124 21.23(c 56.67 Paris Green(a 0.1649 31 . 2 2 ( c ] 56.80 Paris Greeg(a1.. , , 0.1851 35.05(c) 56.81 Zinc Arsenrte(a . . , 0.2088 26.25 41.68 4i:?9 Zinc Arsenite(aj.. . . . . , , 0.2998 4 1 .65( c ) 41.68 41.87 Bordeaux Zinc Arsenite@ , 0.1984 34.21 34.22 20.60 Bordeaux Zinc Arsenite b ] 18.50 0.1788 34.14 Bordeaux Zinc Arsenitejb): 20.72 0.2000 34.19 Bordeaux Paris Green(a) . , 0.3179 30.60 31.76 3i:jo Bordeaux Paris Green(a) 21.90 0.2279 31.71 31.61 18.4 Bordeaux Paris Green(al.. . . . 0.1912 31 . 74_ ( a ) A. 0. A. C. 1915 Referee Sample, ( b A. 0. A. C. 1916 Referee Sample (cj KIOa Sol. with 1 cc. = 0.003000'g.Asn08.
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The results obtained by the iodate method agree closely with those of the modified Hedge procedure. I t was found preferable in the Hedge method t o neutralize the larger part of the hydrochloric acid used t o dissolve the insecticide with 2 5 per cent sodium hydroxide instead of neutralizing all the acid with sodium bicarbonate, as recommended, because this is liable t o cause some loss of arsenic on account of the violent evolution of carbon dioxide. I n order t o apply t h e iodate titration t o the determination of total arsenic in any arsenical insecticide or fungicide, the official distillation process of the A. 0. A. C. mentioned above was employed and the distillation apparatus was arranged as follows: An 8 oz. distilling bulb, provided with a long-stem 50 cc. dropping funnel, was connected t o a 2 4 in. Liebig condenser. The outlet of the condenser was connected t o a 5 0 0 cc. Erlenmeyer flask with a bent glass tube which extended through a 3-hole rubber stopper for about 4 in. The middle hole carried a safety tube 18 in. long which extended within half an inch of the bottom of the flask. The third hole carried a bent tube which extended through a 2-hole stopper t o within half an inch of the bottom of the second 500 cc. flask. Another bent tube just passing through the second hole of this stopper was arranged so t h a t it dipped into the 50 cc. of water placed in a 2 5 0 cc. Erlenmeyer flask which served as a trap. During the distillation the first two Erlenmeyer flasks were surrounded b y cracked ice in a pan. The distillation flask rested in a circular hole cut through a heavy sheet of asbestos board. A wire gauze was placed under the asbestos board. Before starting the distillation 5 0 cc. of water were placed in the first receiver, IOO cc. in the second receiver, and 50 cc. in the third. The sample taken for analysis was weighed directly into the dried distilling bulb and 5 g. of cuprous chloride were added. This was followed b y I O O cc. of hydrochloric acid, sp. gr. 1.19, which washed any material sticking t o the neck into the bulb. Care must be taken t h a t none of the sample or cuprous chloride enters the outlet tube of the distilling bulb. When the volume in the distillation bulb is reduced to about 40 cc., 50 cc. more of the acid are added through the dropping funnel and the distillation is continued until the volume is again reduced t o about 40 cc. Then 2 5 cc. more of the acid are added. The distillation is finished
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when the contents of the bulb are reduced t o not more than 2 0 cc. This procedure ensured the distillation of all the arsenic. After the distillation was completed, the condenser and connecting tubes were thoroughly rinsed into the receivers. The contents of the first two Erlenmeyer flasks were transferred t o a 500 cc. graduated flask. These flasks were rinsed several times, using the entire contents of the third flask which served as a trap. Then each flask was rinsed again with a small quantity of water. All of the rinsings were added t o the graduated flask. Before diluting t o the mark, the solution in the 500 cc. flask was warmed t o 2 0 ’ C. An aliquot of I O O cc. was placed in the titration bottle along with 6 cc. of chloroform and titrated with the potassium iodate solution as described above. If more than 25 or 26 cc. of the iodate solution were required, I O t o 15 cc. of concentrated hydrochloric acid were added before finishing the titration in order t o maintain the proper acidity. For comparison, aliquots were titrated with standard iodine solution according t o the official method of the A. 0. A. C. Using a potassium iodate solution of which I cc. = 0.003000 g. AszOs, the following results were obtained: On account of the physical property of the powdered insecticides which made them adhere t o glass, making
Cc. of KIOa Gram Used for Insecticide Taken 100 cc. Aliquot Paris Green No. 12542... . 0.4782 18.20 Paris Green No. 12489.. 0.6266 23,65 Paris Green No. 12489.. . . . . . . 0 . 5 7 4 5 21.66 Paris Green(a). , . 0.5888 23.33 Paris Green(a). , . , 0.6042 22.85 Bordeaux Paris Green(a) . 0.5865 12.55 13.95 Bordeaux Paris Green(a) 0.6520 13.95 Lead Arsenate-Arsenite(b) . 0.4052 7.20 Lead Arsenate-Arsenite@) , 0.4945 8.80 Zinc Arsenite@). . . . , 0.5486 15.40 Bordeaux Zinc Arsenite@), 0.6106 14.00 Bordeaux Zinc Arsenite(b) , , , 0.6193 14.18 ( a ) A. 0. A. C. 1915 Referee Sample. (a) A. 0. A, C . 1916 Referee Sample.
.. . .. .. .. .. .. . .. . . .. .. . .. ........... ... ... .. .. . . . . . .... . .. . . . . ....... ..... .. . ..
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TOTALARSENICA S AszOa Per cent Iodate Official Method Method 57.06 57.15 56.62 56.64 56.56 56.57 56.92 56.88 56.86 56.80 32.09 32.06 32.12 32.09 32.09 26.65 26.70 26:ji 42.10 42.21 34.39 34.37 34.34 34.38
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their transference difficult, i t was found preferable t o weigh portions of the samples by difference from specimen tubes rather t h a n attempt t o weigh, for example, a n exact 0.5 g. The results of the test analyses by the iodate method given above show excellent agreement with those obtained by the official method. This accurate method is not only quicker, but is simpler than the iodine titration. The very definite and remarkably sharp end-point, the great stability of the potassium iodate solution, and t h e readiness with which i t can be prepared all recommend its use in place of the iodimetric procedure. BUREAUOF CHEMISTRY
U. S. DEPARTMENT OF AGRICULTURE WASAINGTON, D . C.
LABORATORY AND PLANT less decomposition and no discoloration on keeping. It has a n additional advantage in not being deliquescent. It seems desirable for the medical and pharmaceutiThe contradictory evidence given by . certain (‘experts” in a recent sensational murder trial indicates cal professions t o revise their standards for cyanidesa n imperfect realization, even by some chemists, of t h e presumably this has been done in preparing the new fact t h a t commercial potassium cyanide can scarcely Pharmacopoeia. The alkaline cyanide now sold must be said t o exist a t the present time, its place having be much more poisonous t h a n the old material, which been usurped b y the sodium compound. Sodium was no doubt the basis of most of the familiar statecyanide is now widely used as a solvent of the precious ments as t o its lethal effects. It has long been stated metals in ore treatment, in electroplating, and also t h a t 5 grains of cyanide have repeatedly proved fatalas a source of hydrocyanic acid for fumigation, a t which rate a pound would suffice t o kill some 1400 especially in western orchards where gaseous hydro- people. This statement no doubt refers t o cyanide cyanic acid is applied as a n insecticide t o individual of the old type, containing probably 30 t o 3 5 per cent trees which are covered with tents during the process. of potassium cyanide or, say, 1 2 t o 14 per cent of The sodium cyanide of commerce is one of the purest cyanogen. Modern sodium cyanide-commercial a s 50 t o 5 2 per cent cyanogen, technical salts now available, containing 96 t o 98 well as “C. P.”-contains per cent NaCN, with less impurity t h a n is found in or practically four times as much as the material most samples of potassium cyanide sold as chemically formerly sold, and is presumably four times as lethal pure. I wish t o suggest here t h a t chemists might with in its action, so t h a t a pound would suffice for over 5000 fatal doses. advantage make a point of recognizing the use of Nearly thirty years ago, when potassium cyanide sodium cyanide, and call i t by t h a t name in their laboratories. As with so many other alkali-metal was suggested as a practical solvent for extracting salts, we can now use the sodium instead of the,potas- gold from ore, various objections, mainly based on sium compound as a reagent, except in the very few limited experience, were raised: It would not dissolve cases where the potassium ion is essential t o the re- gold in practical quantities; its solution was extremely action, or where there is some marked difference in unstable; it was highly dangerous on account of its solubility. Sodium cyanide not only contains less poisonous qualities; the world’s sources of supply were carbonate and sulfide, but is cheaper, reacts identically altogether insufficient. All these objections have with the salts of silver, copper, zinc, etc., except in proved groundless, Both gold and silver are successconcentrated solutions, and is more permanent in fully and economically extracted; the dilute solution solution t h a n ordinary potassium cyanide, showing “keeps” admirably when handled on a large scale; NOTES ON SODIUM CYANIDE By W. J. SHARWOOD Received January 15, 1917
