Chemical Science. 345 



ammonia, is to be added to the mixture of lime and sulphate before 

 distillation ; for the subcarbonate the chalk is to be dried and 

 sifted. 



The economy of this mode may be readily appreciated by com- 

 paring the commercial value of sulphate and muriate of ammonia, 

 and the proportions of ammonia which they contain. White sub- 

 limed sal ammoniac is worth 4/'. 70c. per kilogramme in commerce : 

 it contains 31 ammonia and GO of acid. The crude sal ammoniac 

 sells for 4/'. 50c. per kilogramme; crude crystallized sulphate of 

 ammonia sells at 80c. the kilogramme ; torrihed at \f. the kilo- 

 gramme ; white and dry at If. 20c. In this state it contains 29 

 ammonia, and 71 of acid. — Ann. de Chimic, xxviii. 171. 



15. Test of tlie presence of Muriatic or Nitric Acid^ or Salts of 

 these Acids. — Fur Muriatic Acid, or Muriates. Put pure nitric acid 

 into a porcelain capsule, and throw to the bottom of it a very mi- 

 nute quantity of finely-divided gold, precipitated from its solution 

 by sulphate of iron ; put into the acid a minute fragment of any 

 muriate, by degrees the gold will be surrounded by a light yellow 

 tint, a certain sign that it is attacked. A fiftieth of a grain of a 

 muriate may be detected in this manner. 



For Nitric Acid or Nitrates. Operating in an inverse manner, 

 the presence of a nitrate in a soluble salt may be ascertained. The 

 gold should be put into muriatic acid as pure and as colourless as 

 possible, and then a fragment of the salt, supposed to contain a ni- 

 trate, added ; sometimes this experiment requires many hours for 

 its completion, if there be but a small quantity of nitrate present. 



This variation of Dr. Wollaston's test, may at times be usefully 

 employed. — Ann. de C/timic, xxviii. 36. 



16. Neio production of Anhydrous Sulphuric Acid. — Professor 

 Gmelin has observed the formation of anhydrous or fuming sul- 

 phuric acid, from common hydrated sulphuric acid, in a new and 

 interesting manner. — 6 lbs. 14-^ oz. of English oil of vitriol, not 

 at all fuming, and of a specific gravity of 1.8435, were heated in a 

 retort, the temperature of the air round the receiver, 8^c., being 

 32° Fahr., and the acid never boiling. Four ounces distilled over, 

 having a strong odour of sulphurous acid ; these were removed, 

 and a clean receiver applied : acid then came over quite destitute 

 of smell, but when 8 ounces had been received, the receiver, before 

 quite clear, became filled with vapours. It was removed and 

 another applied, and cooled by ice : there condensed an acid partly 

 transparent and crystalline, and a portion of solid acid was 

 found in the retort neck. This acid Avas very fuming, it re- 

 mained solid at 12° R. (59°F), and had no smell of sulphurous 

 acid. It formed with sulphur a green compound, and a little sul- 

 phurous acid was disengaged: the green mass in contact with wa- 



