Intelligejice and Miscellaneous Articles. 389 



after adding a few drops of sulphuric acid, the mixture is to be 

 boiled. 



If the fluid contains a nitrate, the blue colour will be discharged, 

 or only rendered yellow if the quantity of nitrate is very minute. Dr. 

 Liebig states that by this process nitric acid may be detected when 

 there is not more than a four-hundredth of it present ; by adding a 

 little common salt to the fluid before applying the heat, even a five- 

 hundredth of nitric acid may be readily detected. — Ann. de Cliimie, 

 XXXV. 80. ■ 



CARBOAZOTIC ACID. 



Dr. Liebig treats fine indigo broken into small fragments, with 

 eight or ten times its weight of nitric acid of moderate strength 

 and in a gentle heat; fresh nitric acid is to be added as long as 

 an extrication of red vapours is occasioned by it. When the liquid 

 has become cold, a large quantity of semi-transparent yellow crystals 

 will be formed, which are to be washed with cold water, then dis- 

 solved in hot, and re-crystallized J these crystals, which Dr. Liebig 

 calls carboazotic acid, have the form of yellow brilliant plates, and if 

 the operation is well conducted, no artificial tannin is obtained during 

 the action of the nitric acid upon the indigo. 



From the mean of several experiments this acid appears to be 

 composed of 



124. atoms of carbon 9375 or 31-5128 



24- a.zote .... 4375 .. 1470G0 



16 oxygen .... 160' .. 537812 



297-3 100- 



This acid may also be obtained by treating silk with ten or twelve 

 times its weight of nitric acid, but it yields much less than indigo. 



Carboazotate of potash is composed of 8379 acid-j- 1621 base. It 

 crystallizes in long yellow quadrilateral needles, which are semi- 

 transparent and very brilliant. It dissolves in 260 parts of water at 

 59 Fahr. and in much less boiling water. Carboazotic acid also forms 

 crystalline salts with soda, ammonia, barytes, lime, magnesia, and 

 also with the oxides of copper, silver, and protoxide of mercury. 



All these salts detonate, and more powerfully when heated in close 

 vessels than when heated in the air ; but with those bases that yield 

 oxygen most readily, the explosion occurred with the least force. — 

 Ann. de Chimie, xxv. 72. 



ANHYDROUS SULPHITE OF AMMONIA. 

 M. Doebereiner combined four volumes of dry sulphurous acid gas 

 with eight volumes of ammoniacal gas, equally dry ; a brownish 

 yellow vajjour was formed, which soon condensed into a light brown 

 substance. On the addition of an atom of water it became colourless, 

 and hydrous crystals were formed. Equal volumes of sul|)hurous acid 

 and ammoniacal gas form supersulphite of ammonia, in which the 

 second atom of acid occupies the place of an atom of water : four 

 volumes of the vapour of water are replaced by four volumes of sul- 

 pliurous acid gas. In the conversion of subciirbonate of ammonia 



into 



