Scientific IntelUg 



SCIENTIFIC INTELLIGENCE. 



L Chemistry and Physics. 

 1. On a (JrystalUzed Hydrate of Hydrochloric acid.— Pmnn^ 

 and PucHOT have observed that, when a saturated solution of hy- 

 drochloric acid gas is cooled to — 21° or —22° C, the dry gas be- 

 ing passed continuously into the liquid, after a few minutes the tem- 

 perature rises to — 18° and an abundant crystallization begins, dur- 

 ing which the temperature remains constant at — 18°. Before the 

 crystallization commences, there is always observed this lowering 

 '' "" ' " ' 1 temperature, which is a phenomenon analogov ' 



saturation, A synthetic experiment showed that, to produce the 



, the water absorbed about its own weight of the gas ; and 



hence showed that the probable formula was HCl. (H2 0)2- In 



crystals, t 



the air the crystals decompose readily, giving off dense fumes of 

 hydrogen chloride. In a flask, kept near 0°, they slowly melt, the 

 temperature remaining at —18°; in one experiment 115 grams of 

 the crystals required an hour and a quarter to melt. Water dis- 

 solves them readily. Since they sink in the solution where they 

 are formed, they must be denser than it. They set free the gas in 

 melting, and hence must contain more of it than the mother liquors. 

 In the analysis, a known weight of the drained crystals was treated 

 with a definite quantity of distilled water, in amount sufficient to 

 prevent the evolution of gas. The chlorine was then determined 

 in the solution, and from this the ratio between the HCl and the 

 HgO could be calculated. In the first two determinations, the 

 ratio was 1:2-19; in the second it was 1:2-085 and 1:2-076. 

 Hence the authors conclude upon the formula HC1.(H3 0)2; this 

 is the best defined hydrate of hydrochloric acid yet observed. A 

 mixture of snow two parts and hydrochloric acid one part gives 

 a temperature of -32*C.; or of -35° if the materials are pre- 

 viously cooled. — G. a., Ixxxii, 45, Jan, 1876. g. r. b. 



2. O/i the Decomposition of Water by jPiati/mm.—SAim^E Claike 

 Deville and Debray state that if potassium cyanide be heated in 

 a glass tube to 500° or 600°, in the vicinity of a boat full of warm 

 water, the tube having been previously exhausted, the pressure rises 

 to half an atmosphere, and remains constant for hours; but if, be- 

 fore the operation, some platinum sponge has been mixed with the 

 cyanide, hydrogen is abundantly evolved, and a potassio-platinum 

 cyanide is formed. This hydrogen contains from ^ to 12 per cent 

 of carbonous oxide, produced according to the following reaction, 



(KCN)3+(H2O)^-K2CO3+(NH3)2-4-H3+C0 

 If the principal reaction in the foregoing experiment be written— 



(KCy), + (H,0)2=PtCy,(KCy), + (KOH),+H_, 

 it would appear as if the platinum decomposed water under the in- 

 fluence of the potassic cyanide. But the authors show from ther- 

 mal considerations that the potassium hydrate formed is really the 

 important product ; that in its formation the greatest amount ot 



