590 Van Name and Huff — Hypophosphates. 



previously charged with water and sodium carbonate, 

 thus making the process continuous. The product, acid 

 sodium hypophosphate, is found in part as a crystalline 

 precipitate in the first jar ; the rest is recovered by con- 

 centrating the mother liquor. It is purified from accom- 

 panying phosphates and phosphites by simple recrystal- 

 lization from hot water. 



This form of apparatus requires the minimum of atten- 

 tion, and* all the manipulations and adjustments are very 

 easily made. Moreover, the sodium carbonate solution 

 has distinct advantages over the sodium acetate which 

 has been generally used in methods of this class hitherto. 

 The alkalinity of the carbonate solution prevents hydrol- 

 ysis, and the proper point for renewing the solution can 

 be determined by a simple and easy test. The carbonate 

 is also more economical, not only on account of its cheap- 

 ness, but also because it eliminates waste. No more of 

 the salt is used than is actually required to react with the 

 phosphorus oxy-acids, while with sodium acetate, which 

 liberates acetic acid, the lack of any convenient method 

 for determining the end point makes it easy to err, either 

 by deferring the renewal of the solution too long, thus 

 permitting excessive acidity to develop, with consequent 

 loss of hypophosphate, or by interrupting the action too 

 soon, which results in the loss of the unused excess of the 

 sodium acetate. 



In our experiments the room temperature ranged 

 between 10° and 15° C. and the yields between 10 and 16 

 per cent of the theory. No marked relation between the 

 average temperature and the magnitude of the yield was 

 observed. A charge of 250 grams of anhydrous sodium 

 carbonate lasted, as a rule, for a period of seven to ten 

 days ; the complete oxidation of the sticks of phosphorus 

 required, on an average, eight or nine weeks. 



