

of Anhydrous Sulphuric Acid. 245 



that the not fuming (so called in English) oil of vitriol yields 

 at a certain period of the distillation fuming acid. I heated in 

 a retort, connected with a receiver, 6 pounds 14^ ounces Eng- 

 lish oil of vitriol, of a specific gravity, = 1.S435 at + 10^° R. 

 which was not the least fuming. The acid never came to 

 boiling ; the temperature of the air was 0° R. four ounces hav- 

 ing distilled, having a strong smell of sulphurous acid, the re- 

 ceiver was emptied, cleansed, and applied anew. When eight 

 ounces of an acid, which was quite destitute of smell, had 

 distilled over, the receiver, which had hitherto been perfectly 

 transparent, was suddenly filled with vapours. It was re- 

 moved, and another dry receiver applied, which was now 

 surrounded with powdered ice. There was condensed an acid 

 partly not transparent, partly transparent and crystalline ; a 

 good deal of the solid acid was found in the neck of the re- 

 tort. This solid acid was exceedingly fuming like that pro- 

 duced from the fuming oil of vitriol ; it remained solid at 

 -f- 12° R., and had no smell of sulphurous acid. When 

 brought in contact with a certain quantity of sulphur, in a 

 close air-tight glass vessel, a green compound, having the 

 colour of muriate of chrome, was formed, and a little sulphu* 

 rous acid was disengaged. This green mass being brought 

 in contact with water, a very great heat was evolved, sulphu- 

 rous acid formed, and sulphur dissolved. When the solid 

 acid was brought in contact with water, diluted acid was form- 

 ed, but no sulphurous acid. This diluted acid being saturat- 

 ed by potash, and evaporated to crystallization, no nitre was 

 formed, nor were nitrous vapours produced by heating the 

 dry mass with concentrated sulphuric acid. The specific 

 gravity of the acid left in the retort, which was now sensibly 

 fuming, was found = 1.8503 at 4- 13 r R, the specific gravi- 

 ty of the acid which distilled over, = 1.4309 at -f- lli° R.* 

 This experiment being repeated with the same acid, the same 

 result was obtained. But it may happen, that the moment at 

 which the fuming acid is formed is overlooked ; in the experi- 

 ments just now mentioned, it was not formed, but in the first 

 half of the third day, (during the two first days, from seven 



• The specific gravities were determined by means of a small bottle, 

 provided with a plate ground upon its neck. 



