364 On the AUeralion which Sulphuric Acid 



Both can be rendered more dense, and" in the same degree, in 

 tlie vacuum of the pneumatic machine. 



Both form soluble salts which have the strongest resemblance. 



Both, as well as their salts, are decomposed by nitric acid aided 

 by heat, and give sulphuric acid and sulphates. 



The difference between them consists in this, that the sulpho- 

 vinoHs acid and its salts contain a volatile oil, which escapes at 

 a high temperature, and is partly decomposed. The hypo-sul- 

 phuric acid, on the contrary, is converted by heat into sulphurous 

 acid and sulphuric acid without yielding oil, and the hypo-sul- 

 phates do not carbonize at a red heat. 



From these facts, it results that sulphuric acid mixed with 

 alcohol is decomposed without the assistance of heat ; that it 

 abandons the oxygen, and gives birth to a particular acid. Du- 

 ring etherification, the action of sulphuric acid is not confined to 

 determining the formation of w;tter, as Fourcroy and Vauquelin 

 have announced, and the theory of ether ought therefore to be 

 modified. The new acid has the greatest affinity to the hypo- 

 sulphuric acid, and only differs from it in the volatile oil with 

 which it is combined. 



On leaving sulphuric acid in contact with birch saw-dust, or 

 oil of lavender, it produces an acid which forms with barytes and 

 the oxide of lead very soluble salts, which analysed are also re- 

 duced into sulphates. 



As soon as we received an account of the experiments of 

 M. Vogel we hastened to repeat them. 



We made accordingly a mixture of equal parts of sulphuric 

 acid and alcohol, and exposed it to heat until sulphurous acid 

 began to manifest itself. The residue saturated with lime and 

 filtered, furnished by evaporation a salt in small flakes; but to 

 obtain more precise results on the nature of sulphovinous acid 

 we transformed this salt into sulphovinate of barytes, decompos- 

 ing it by a slight excess of that base, and passing afterwards 

 through the filtered solution a current of carbonic acid gas. By 

 a crystallization effected in the course of twelve hours we ob- 

 tained the salt crystallized in small pearly scales of a square 

 form ; but by a spontaneous evaporation, we obtained beautiful 

 four-faced rhoniboidal prisms terminated by a pyramid with four 

 faces corresponding to those of the prism. These crystals have 

 a very beautiful appearance, and are not affected by exposure to 

 the air ; in the receiver, however, by the side of the concen- 

 trated sulphuric acid, they become opaque in the course of twenty- 

 four hours, and aI)andon a certain quantity of water. One hun- 

 dred parts of salt ^iiinply dried in the air have lost by calcination 

 45-07; but a hundred ))aits of the same salt dried in the re- 

 teiver have only lost 4l"5. The 



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