410 EXPERIMENT STATION RECORD. 



Method of preparing a strictly neutral ammonium citrate solu- 

 tion, A. D. Cook (Jour. Amer. Ghem. Soc, 20 (1898), No. 8, pp. 585, 

 586). — The difficulty of preparing a strictly neutral ammonium citrate 

 is briefly discussed and the following method is recommended: 



"Seven hundred and forty grams of commercial citric acid is carefully -weighed 

 out and placed in a 4-liter graduate containing 1,900 cc. of 10 per cent ammonium 

 hydroxid. With a suitable glass rod the citric acid is thoroughly and vigorously 

 stirred until the citric acid has all dissolved. Distilled water is now added until 

 the meniscus reads 4,000 cc. The solution is again stirred and carefully transferred 

 to a large porcelain evaporating dish. The solution is allowed to stand over night 

 and in the morning large oval crystals are noticeable on the sides of the 4-liter grad- 

 uate, and invariably the solution when tested for neutrality will be found strictly 

 neutral. If the solution is not vigorously stirred sufficient heat will not be evolved 

 to drive off the excess of ammonia, and when tested will be fouud to be slightly 

 alkaline, but by resorting to vigorous stirring a strictly neutral reaction will be 

 obtained. The solution, after being transferred to the reagent bottle, is brought to 

 the required temperature, 20° C, and distilled water added until the specific gravity 

 is 1.09. On testing the neutrality of this solution, both with coralline and coch- 

 ineal as indicators, it will be found unnecessary to alter its neutrality iu the least 

 degree, the solution being strictly neutral." ' 



A method for determining perchlorate in sodium and potas- 

 sium nitrates, N. Blattner and J. Brassetjr (Bui. Soc. Chim. 

 Paris, 3. ser., 19 (1898), No. 12, p. 539; and Ghem. Ztg., 22 (1898), No. 

 59, pp. 589, 590). — The method recommended is as follows: Determine 

 chlorin by the usual method in the original substance, then dry and 

 pulverize 5 or 10 gtn. of the nitrate. Mix with 8 to 15 gm. of pure lime 

 obtained by calcining pure precipitated calcium carbonate. Place the 

 mixture in a covered platinum or porcelain crucible and heat in the flame 

 of a Bunsen burner for 15 minutes. After cooling remove the contents 

 of the crucible to a flat-bottomed flask, dissolve in dilute nitric acid 

 (free from cblorids), and determine chlorin in the solution by means 

 of silver nitrate either in acid solution, according to Volhard, or in 

 a solution neutralized by calcium carbonate, or by weighing the silver 

 chlorid. By this means chlorin iu chlorids, chlorates (if any are pres- 

 ent), and perchlorates are determined, from these data the amount of 

 perchlorates present may be calculated. 



The determination of phosphoric acid in superphosphates, 

 L. VlGNON (Gompt. Mend. Acad. Set. Paris, 126 (189s), No. 21, pp. 1522, 

 1523; 127 (1*98); No. 3, p. 191). — The determination of water-soluble 

 and citrate-soluble phosphoric acid in 1 sample of bone superphosphate 

 and 2 samples of mineral superphosphate are reported. The percent- 

 ages of soluble phosphoric acid found were 14.32, 11.13, and 10.20 per 

 cent, respectively. The percentages of citrate- soluble phosphoric acid 

 were 0.77, 0.27, and 3.1, respectively, when the solution was allowed to 

 stand 8 hours before filtration and 1.08, 0.45, and 3.18, respectively, 

 when allowed to stand 15 hours before filtration. When phosphoric 



1 Compare De Roode's method, Jour. Amer. Ghem. Soc., 17 (1895), p. 47 (E. S. R., 6, p. 



864J. 



