The pharmacopoeial tincture contains about 6.56 grams of free iodine and j grams of potassium iodide in I O O cc. The range of variation (1.97t o 9.26 grams per I O O cc.) is certainly remarkable. What real valid excuse can be offered for either of the above extremes? Furthermore, is there any substantial reason for some of the other variations? The permissible variation from the standard must he met sooner or later. Shall i t be stringent or reasonable? If reasonable, shall the variation be j per cent or I O per cent or 2 0 per cent? ('onsidering t h a t the adjective " about" qualifies the ;tmount of free iodine t h a t should be present in the tincture, about 60 per cent exceed a j per cent variation, 40 per cent a I O per cent variation and 18 per c m t a 2 0 per cent variation. I do not believe many manufacturers will contend for or advise a 20 per cent variation in that i t would not only savor of carelessness hut actually encourage it. I s then a I O per cent variation either way from the standard, reasonable, fair and just to the manufacturer, the consumer, the physician, etc., or is i t desirable t o be more stringent? Suggestions are invited either in the columns of TITISJ O U R N A L or otherwise. The free iodine is the cssential factor of this tincture but the potassium iodide and percentage of alcohol must also be considered. The conditions noted above relative t o the variability of the free iodine also hold for potassium iodide. The variation ranges from no potassium iodide to 6.82 grams per r o o cc. Discussion in this connection is also invited. DRUG DIVISION B U R E A UOF CHEMISTRY 1;. s. D E P A R T M E K T AGRICULTURE
THE APPLICATION OF FOLIN'S METHOD FOR THE DETERMINATION O F AMMONIA TO FERTILIZERS B y OTTO FOLIN AND A. W. BOSWORTH
Received March 3, 1913
The determination of ammonia in commercial fertilizers is usually mad.e b y distilling with magnesium oxide.1 I n Folin's method for the determination of ammonia in urine* the ammonia is removed by a strong air current a t room temperature. This method is generally applicable t o all kinds of materials and has the advantage of being both rapid and reliable. I t has been used for the determination of ammonia in meat3 and in cheese.4 The speediness of the determination has been greatly increased by the microchemical modification recently published by Folin and Macu1lum.j By this new method a n ammonia determination can be made in less than half a n hour. This method is applicable to the determination of ammonia in fertilizers. Applied to such products the method is as follows: 'Two grams of fertilizer are placed in a I O O cc. graduated flask, about j o cc. of water added and then 25 cc. of approximately normal hydrochloric Bureau of Chemistry, U. S . Department of Agriculture, Bull. 107 (revised). a Folin, Z . Dhvriol. Chem., 37, 161. Pennington and Greenber, J . A m . Chem. Soc., 32 561. 1 Bosworth nnd Winter. Rureau uf Chemistry, TJ. S . Ilepnrtment o f Agriculture, Bull. 152. 6 Folin and Maculluni, J . B i d Clzum., 11, ,523.
acid. The volume is now made up to I O O cc. with water, the contents of the flask are shaken, and after standing a few minutes are shaken a second time. The flask is now allowed to stand until the heaviest of the undissolved particles have settled. Five cc. of the supernatant liquid are withdrawn by means of :L pipette (filtering is not necessary) and transferred to the tube of the Folin apparatus. Two cc. of a saturated solution of potassium oxalate, a few drops of kerosene and finally z cc. of a saturated solution of potassium carbonate are added. The apparatus is immediately closed and air passed through for I O to 20 minutes. The ammonia is collected in a flask or test tube which contains z o cc. of seventieth normal hydrochloric acid. If the air current is produced by a blast the ammonia is collected in a flask and 2 j cc. of water are added to the 2 0 cc. of acid in order to increase the volume and thus prevent the loss of ammonia. After the distillation, the contents of the flask, or test tube, are titrated back with seventieth normal sodium hydroxide, using alizarin red as indicator. The percentage of nitrogen as ammonia is found by subtracting the number of cubic centimeters of alkali used from the number of cubic centimeters of standard acid used, and dividing the difference by five. Diagrams of the apparatus with descriptions have been given b y Folin and Farmer.1 The method as given has been tried on several samples of fertilizers and the results obtained, together with those obtained by the magnesium oxide method, are given in the table below. The two sets of results were obtained b y different persons, working in different laboratories and the results by the Folin method were obtained several months after those by the magnesium oxide method. The samples are representative of what may be found on the market. NHsby NHaby Sample the Folin distilling Total number method with MgO nitrogen 1 2 3 4 5 6 7 8 9 10 I1 12 13 I4 15
16 17 18 19 20 21 22
0.00 0.08 0.11 0.03 0.03 0.08 0.20 0 06 0.22 0.15 0.29 0.31 0.43 0.70 0.69 0.90 1.04 1.37 1.47
0.00 0.05 0.06 0.08 0.13 0.13 0.17 0.17 0.20 0.20 0.38 0.39 0.42 0.65 0.77 0.89 1.07 1.35 1.44
1.43
1.59
2.31 2.72
2.33 2.58
2.10 3.20 8.24 5.11 1.51 5.25 2.07 1.13 3.43 3.09 3.13 2.46 1.09 4.71 2.83 2.29 2.16 2.58 3.99 4.02 4.07 3.08
Chief source of nitrogen nitmte, organic
organic nitrate, orgnnic organic nitrate, organic
organic, ammonia nitrate, organic. ammonia I' ammonia organic ' I nitrate, organic. nnimr)iiin organic, ammonia '' nitrate " urgiinic, xmniABORATORY
IIARVARD MEDICAL SCIIOIX
Rosro?i 1
I'olin and Farmer, J. Biol. Chem., 11, 493.
