Chemistry and Physics. 331 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Use of Calcium Carbide for the Determination of Moisture. 

 — This application of calcium carbide has been discussed by 

 Masson. Difficulties occur in the ordinary methods of determin- 

 ing moisture from the fact that other vapors besides water may 

 be given off by the substance, or that the substance is oxidized 

 and gains weight when heated in the air to expel its moisture. 

 Calcium carbide has the advantage that water is the only ordi- 

 nary substance that will react with it, and the acetylene pro- 

 duced by the reaction can be readily measured. Hygroscopic 

 organic substances are mixed with an excess of finely powdered 

 carbide, when the reaction takes place quickly without artificial 

 heating, and the gas evolved may be measured or its pressure 

 determined by means of a manometer. The method has been 

 applied for the determination of moisture in wool, explosives, 

 petroleum, etc. The author has studied the application of the 

 method to the determination of water of crystallization in salts, 

 and finds that salts may be roughly divided into four classes in 

 respect to their behavior with calcium carbide. In the first are 

 those, such as sodium carbonate and sodium sulphate, which 

 react at once and completely. In the second class are those that 

 react rapidly and completely only on heating, such as barium 

 chloride. The third class, which includes such salts as copper 

 sulphate and the alums, react, either in the cold or on heating, in 

 such a way as to lose only a part of their water, leaving a 

 hydrated residue which belongs to the fourth class, characterized 

 by being quite stable towards carbide even at 1 70° C. It is a 

 noteworthy fact that ammonium salts do not lose ammonia, nor 

 do crystalline acids react as such, when these are heated with the 

 carbide and calcium hydroxide present as a result of the acety- 

 lene production. This is to be attributed to the complete 

 absence of free water. It is interesting to notice that various 

 observers have found that 18 ms of water corresponds to 10*5 OC of 

 acetylene at standard conditions, while the theoretical volume is, 

 of course, 11"2 C0 . — Chem. JVews, ciii, 37. h. l. w. 



2. Action of Water upon Phosphorus Pentoxide. — Various 

 statements are found in the literature concerning the products of 

 this reaction, that is, whether metaphosphoric acid, HPO s , the 

 pyro- acid, H 4 P 2 7 , the ortho- acid, H 3 P0 4 , or mixtures of these 

 are first formed. Balareff has now investigated this matter by 

 allowing pure sublimed P 2 6 to deliquesce very slowly, and more 

 rapidly in more or less moist air, and also by throwing it directly 

 into water. In every case where the product was examined imme- 

 diately after deliquescence, only metaphosphoric acid, HP0 3 , 

 could be detected. In about 18 hours some of these products 



