Van Name and Huff — Hypo-phosphates. 587 



Art. XXVI. — On the Preparation of Hypo phosphates; by 

 K. G. VanName and Wilbert J. Huff. 



(Contributions from the Kent Chemical Laboratory of Yale Univ. — ccciii.) 



Hypopkosphoric acid and its salts are usually prepared 

 by the oxidation of yellow phosphorus. This may be 

 accomplished either by the slow action of the air upon 

 sticks of phosphorus partly submerged in water (the 

 original method, due to Salzer 1 ) , or by the gradual addi- 

 tion of the phosphorus to a warm acid solution of copper 

 nitrate (Corne 2 ), or of silver nitrate (Philipp 3 ). It may 

 also be prepared by the electrolytic oxidation of copper 

 phosphide used as anode in dilute sulphuric acid (Rosen- 

 heim 4 ). In all these cases phosphoric and phosphorous 

 acids are formed at the same time, but on converting the 

 three acids into their sodium salts the difficultly soluble, 

 acid sodium hypophosphate, Na ? H 2 P 2 R .6HoO, separates 

 first from the solution, and can be purified by recrystal- 

 lization. This salt is consequently the usual starting 

 point for the preparation of hypophosphoric acid and its 

 compounds. 



The first of the above reactions is the one which has 

 received the most attention, and is the basis of several of 

 the methods described in the literature. 5 Methods of this 

 class are necessarily slow, but have compensating advan- 

 tages in economy and simplicity of operation, including 

 the advantage that the sodium salt just mentioned, which 

 is generally desired, can be obtained directly, without the 

 need of special treatment to remove copper or silver. 

 This reaction is the one employed in the improved appa- 

 ratus and procedure which we describe below. 



In Salzer 's original method the phosphorus was 

 immersed in water or a dilute solution of sodium chloride. 

 In either case the liquid soon becomes strongly acid, and 

 unless the process is interrupted rather frequently for 

 renewal of the liquid and recovery of the hypophosphoric 

 acid already formed, some of the acid is likely to be lost 



1 Ann. Chem., 211, 1, 1882. 



-Jour. Phar. et Chim., (5) 6, 123, 1882. 



3 Ber. chem. Ges., 16, 749, 1883. 



4 Ber. chem. Ges., 43, 2003, 1910. 



5 Salzer, loe. cit. ; Bansa, Zs. anorg. chem., 6, 128, 1894; Cavalier and 

 Cornec, Bull. Soc. Chim., (4) 5, 1058, 1909. 



