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METHODS OR OBTAINING SULTHUKIC ACID.

hidrogen gases. It combines with nitrous acid, and forms acompound which dissolves silver, but scarcely any other metal.(Page 158.) It is decomposable by a number of inflammablesubstances which attract its oxigen. If brought in contact withany vegetable or animal matter, it is partially decomposed, and aquantity of carbon is disengaged which gives the acid a brownor black colour. It oxidates and dissolves a number of the me-tals, either affording to them part, of its oxigen, or enabling themetal to decompose the water which is present. It attracts waterfrom the atmosphere,

METHODS OF OBTAINING SULPHURIC ACID.

The processes employed for obtaining sulphuric acid may bereduced to two, namely; to unite sulphur to oxigen, or to se-parate the acid from its combinations met with in nature.

The first method is made use of in this country; for whichpurpose peculiar buildings or apartments, with their insides linedwith lead are constructed. In these apartments sulphur is burnt,in order to absorb oxigen from the air during its combustion.But as the sulphur would not burn or become fully oxidated in aconfined quantity of air, ^ to T 'y of nitrate of potash is previouslymixed with it in order to make it burn with vivacity, or to gainoxigen from the nitric acid. The sulphuric acid which is formedis absorbed by a stratum of water at the bottom of the chamber.The water, after being sufficiently impregnated, is exposed toheat in large glass retorts, so as to deprive the acid of the super-fluous water, the sulphureous acid, and nitrous gas, with whichit is mixed.

Rationale. ..The theory of this process has been noticed al-ready, vol. I. p. 145.

Remark. ..The sulphuric acid obtained in this manner is notperfectly pure, but always contains small quantities of sulphateof lead and sulphate of potash; from which it may be freed byre-distillation.