INFLAMMABLES, 309 



(b.) When pure; colorless, limpid, inodorous; intensely sour, even 

 when largely diluted with water. 



(c.) Sp. gr. as already stated, 1.850, or (Ure,) 1.842 ; ac- 

 cording to Dr. Thomson, 1.847 ; if heavier, it may contain sulphate 

 of lead, or sulphate of potash, or both ; 2 J per cent, of sulphate of 

 potash gives it the sp. gr. of 1.860, and Dr. Ure states* that the best 

 acid of commerce contains from J to f of 1 part in 100, of foreign 

 matter, which is sulphate of lead, in the proportion 4, to sulphate of 

 potash l.f 



(d.) Its purity is decided by saturating it by an alkali. Dry car- 

 bonate of soda, 100 grains, neutralizes 92 grains of pure liquid sul- 

 phuric acid, and 100 of the acid require 108, or 108.5 of the car- 

 bonate. J Henry. 



(c.) Produces heat, when mingled with water in every proportion ; 

 4 acid -f 2 water =300 Fahr. ; or better, 2 acid to 1 water, or 

 by measure, If, or 1 acid to 1 water. 



Place a thin glass tumbler in a dish pour in the water provide 

 a thin glass tube, 8 or 10 inches long, and fill it two thirds with 

 colored water, add the acid in a slow stream, stirring with the glass 

 tube, and soon after, the water in the tube will boil, and another 

 tube, filled with alcohol, will also be made to boil. 



Explanation. Increase of specific gravity, and diminution of ca- 

 pacity for heat. 



Two by measure, of acid -f-1 of water, starting from 50 =300, 

 and the concentration =^. 



(/.) With ice. Ice 1-f- acid 4=212. 



ice 4-f- acid 1 produce intense cold. 



In both instances, the affinity of the acid for the water produces 

 fusion, as the two cannot unite while the water is solid. The excess- 

 of acid then goes, in the first case, to produce heat with the water form- 

 ed ; in the second case, there being no more acid than is wanted for 

 the fusion, cold is produced, upon the general principle that fluidity 

 requires heat, and that the absorption of heat produces cold. 



(g.) Absorption of water from the air. Rapid, especially if ex- 

 posed with a large surface ; in one day 3 parts became 4, and 1 oz. 

 in twelve, months gained 6^ ; a drachm gained in five successive days, 

 68, 58, 39, 23, and 18 grains, and in five days more only, 5, 4, 3, 4 ; 

 in one case, in fifty six days a drachm became 6 J drachms. 



* Diet. 2d Ed. p. 91. 



t The acid of commerce often contains 3 or 4 per cent, of salts, and sometimes 

 more arising from the use of nitre, to remove the brown color; evaporation in a pla- 

 tinum dish gives a prompt result, and if there are more than 5 grains in 500, the acid 

 is sophisticated. Ure. 



\ These numbers do not correspond with the equivalents of sulphuric acid and 

 carbonate of soda, as they stand in our modern works. 100 acid should neutralize very 

 nearly 110 of carbonate soda. (49 liq. sul. acid : 54 carb. soda : : 100 S. A.: 110.2 

 C. S.) Communicated. 



Seventy three acid to twenty seven water, or very nearly 3 acid to 1 water. Ure. 



