SULPHURIC ACID 329 



hydrochloric, sulphuric, phosphoric, and hydrochloric acids 

 are the most powerfully corrosive. Nitric acid does not so 

 readily re-dissolve the precipitated albumin, and hence is 

 scarcely so penetrating as other mineral acids. Sulphuric 

 acid, when applied to the skin or swallowed, causes blacken- 

 ing or browning of the parts with which it comes in contact ; 

 nitric acid leaves a yellow stain ; hydrochloric, a white film 

 of precipitated albumin. 



Sulphurous, boric, benzoic, lactic, and salicylic acids, are 

 used for their antiseptic rather than for their special acid 

 properties. Carbolic acid is also an antiseptic, and an alco- 

 hol rather than an acid. Arsenious acid is not a true acid, 

 but an anhydride. Tannic and gallic acids, although they 

 have acid reactions, are glucosides. The striking actions of 

 hydrocyanic acid distinguish it from all other acids. These 

 acids will accordingly receive separate notice under their 

 English names. 



SULPHURIC ACID 



ACIDUM SULPHURICUM. Oil of vitriol. An acid produced 

 by the combustion of sulphur or pyrites, and the 

 oxidation and hydration of the resulting sulphurous 

 anhydride by means of nitrous and aqueous vapours. 

 It should contain about 98 per cent., by weight, of 

 hydrogen sulphate. H 2 SO 4 . (B.P.) 



PROPERTIES. The strong acid of commerce is oily-looking, 

 colourless, odourless, with an intensely acid and acrid taste. 

 It freezes about 30 Fahr., boils at 640 Fahr., absorbs 

 moisture from the air, and hence, if kept in unstoppered 

 bottles, speedily becomes diluted. Specific gravity 1*843. 

 It has great affinity for water, mixes with it in all proportions 

 with evolution of much heat. Thus, combining with water 

 and albumin, it decomposes and chars organic substances 

 and soft animal tissues. When heated with charcoal, 

 sulphur, or metals, it rapidly parts with oxygen, and is 

 converted into sulphurous acid. 



The acidum sulphuricum dilutum, or medicinal acid, 

 should contain 13-65 per cent, of hydrogen sulphate. The 



