322 Intelligence and Miscellaneous Articles. 



acids in atomic proportions. Its preparation is not attended with 

 success unless certain precautions are taken. It is particularly ne- 

 cessary to avoid every trace of moisture, for if it be present, this 

 compound decomposes very rapidly even when it is formed, and if not 

 already formed, should one of its constituents contain the least 

 moisture, the experiment will not succeed. 



M. Rose therefore conducts the gaseous sulphurous acid into a 

 cooled receiver, then passes it througli a tube of at least four feet 

 long and filled with chloride of calcium which has been recently 

 fused. This tube communicates with a glass vessel containing the 

 anhydrous sulphuric acid. This vessel is cooled to about the free- 

 zing point of water, but not below it, in order that the product may 

 not contain any free liquid sulphurous acid. As soon as a certain 

 quantity of liquid is formed it must be poured off from the excess 

 of solid sulphuric acid into a small and well-stopped glass vessel. 

 The chloride of calcium in the tube will serve for the preparation 

 of only a small quantity of this compound, and must be re-heated to 

 redness before it is again used. 



The liquid thus obtained exhales when in contact with the air ex- 

 tremely powerful fumes resembling sulphurous acid. It volatilizes rea- 

 dily, the residue being a very small quantity of liquid sulphuric acid. 

 If a very small portion of water be put in contact with this liquid, it 

 immediately produces a lively effervescence with a disengagement of 

 sulphurous acid. Dry ammoniacal gas passed into this liquid, a mixture 

 of anhydrous sulphate and sulphite of ammonia is obtained of a yel- 

 lowish colour, and soluble in water : its solution on the addition of hy- 

 drochloric acid disengages sulphuric acid, but does not precipitate 

 sulphur, which only takes place when the liquid is boiled. A solution 

 of nitrate of silver affords a precipitate, which is at first white, be- 

 comes yellow, brown, and finally black, particularly by ebullition. 

 M. Rose in the analysis of this compound has ascertained the precise 

 quantity of sulphuric acid, but not that of sulphurous acid, although 

 he endeavoured to determine the latter in many different modes ; he 

 was therefore obliged to calculate the quantity of this acid from the 

 loss. The results of the analysis of four distinct preparations are 

 placed according to their age, for it is found that the compound 

 contains more sulphuric acid when it is not analysed immediately 

 after its preparation, a little sulphurous acid being separated ; and 

 on the contrary, more sulphurous acid in the opposite case, when 

 it may contain a little free sulphurous acid. 



Thus this combination does not contain, as the author supposed 

 before it was analysed, sulphurous and sulphuric acid in the pro- 

 portions necessary for the formation of anhydrous hyposulphuric 



