Sir Humphry Davy, Bart. 98 



round its axis by the approach of a magnet, realised by the 

 ingenuity of Mr. Faraday, had been anticipated and even 

 attempted by Dr. Wollaston in the laboratory of the 

 Royal Institution. 



{To be continued.) 



Article II. 



On the Formation of Sulphuric Acid. By Thomas Thomson, 

 M. D. F. R. S. L. and E. &c. Regius Professor of Che- 

 mistry in the University of Glasgow. 



It is well known that sulphuric acid is manufactured in 

 this country by the combustion of sulphur. The sulphu- 

 rous acid formed is passed into large leaden chambers, 

 where it comes in contact with nitric acid and a small 

 quantity of water ; the fumes of the nitric acid being sent 

 into the leaden chamber at the same time with the sulphu- 

 rous acid. Now, whenever any sloping part occurs in the 

 leaden chamber at some height above the floor which is 

 covered with water, there is a deposit of a white saline 

 matter. 



This saline matter is in small scales. It has an exces- 

 sively acid taste. When exposed to the air it gradually runs 

 into a liquid, which is pure sulphuric acid. When thrown 

 into water a violent effervescence takes place, nitrous gas 

 is given off in abundance, and a solution of sulphuric acid 

 remains. This saline matter has been repeatedly examined. 

 Davy considered it to be a compound of nitric acid and sul- 

 phurous acid. Dr. Henry examined it some years ago, and 

 concluded from his experiments that it is a compound of 

 hyponitrous acid and sulphurous acid. 



By the kindness of Mr. Tennant I have had repeated 

 opportunities of examining this matter in a state of great 

 purity. I have subjected it to various experiments, and have 

 been led to form a different opinion from that entertained 

 by Dr. Henry of its composition. How far the experiments 

 which I shall detail warrant that opinion, I leave to prac- 

 tical chemists to determine. The analysis is not quite satis- 

 factory, because we cannot determine experimentally the 

 quantity of water present. 



