New Formation, (>/ Anhydrous Sulphuric AcicL 315 



PROFESSOK GMELIN ON A NEW FORMATION OF ANHYDROUS 

 SULPHURIC ACID. 



It has been an opinion hitherto received, that anhydrous 

 sulphuric acid can be obtained in no other way than by de- 

 composing in a distillatory apparatus such sulphates as, when 

 heated, give off their acid — such as calcinated iron-vitriol. It 

 is generally known that the fuming oil of vitriol from Nord- 

 hausen is procured in this way. I have found 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 English oil 

 of vitriol, of a specific gravity, = 1-8435 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 having dis- 

 tilled, having a strong smell of sulphurous acid; the receiver 

 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 trans- 

 parent, was suddenly filled with vapours. It was removed, 

 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 retort. This 

 solid acid was exceedingly fuming, like that produced from the 

 fuming oil of vitriol; it remained solid at +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 sulphurous acid was disengaged. This 

 green mass being brought in contact with water, a very great 

 neat was evolved, sulphurous acid formed, and sulphur dis- 

 solved. When the solid acid was brought in contact with 

 water, diluted acid was formed, but no sulphurous acid. This 

 diluted acid being saturated 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 scnsiblij fuming, was found = 1*8503 at +13° 

 R. ; the specific gravity of the acid which distilled over, = 

 1*4309 at + Hi" R.* This experiment being rej)eated with 

 the same acid, the same result was obtained. But it may hap- 

 pen that the moment at which the iiiming acid is formed is 

 overlooked: in the experiments just now mentioned it was 



• The ^iiciific gravitic.-. were (lului'miiicd l)y nicaii'i of a small liolllc, [»ro- 

 vidcd with a [ihitf urmind iijion its neck. 



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