8 Volatile Alkali a compound Subftance. [Book VF 



never found in a fimple ftate. It is met with in 

 nature only compounded with other bodies, in nitrous 

 ammoniac, or in common fal ammoniac, which is 

 fomedmes found in the neighbourhood of volcanoes,, 

 or coal mines which have burnt for a long time. 

 The volatile alkali of commerce is chiefly produced 

 from bones. This alkali is very different in its. 

 properties from the other two; its volatility is fa 

 great, that under the ordinary prcflure of the at- 

 mofphere it is continually flying off in a very pun- 

 gent vapour. It is fold in the mops under the name 

 of fmelling falts, fal volatile, or fpirit of hartmorn. 

 The proceis of putrefaction in animal matters, and 

 in fome vegetables, particularly cabbages, throws it 

 off into the air, together with other volatile matters^ 

 \vhich in fome meafure difguife its fmell. Volatile 

 alkali is now proved to be a combination qf two other 

 fubftances, namely, the bafes of the azotic and hy- 

 drogen gaffes. M. Berthollet has found by analyfis; 

 that -1,000 parts of volatile alkali confiit of about 

 807 parts of azote, combined with 193 of hydrogen. 

 The volatile alkali of the mops, that is in its mild 

 and concrete ftate, when heated to a certain degree, 

 aflumes the form of vapour, but by a diminution of 

 the heat returns again to the concrete form. Volatile 

 alkali, however, deprived of the fixed air which ren- 

 dered it mild, is capable of receiving a permanently 

 elaftic form ; in which ftate it is called alkaline air. 

 When a mixture of alkaline air and marine acid air 

 was made by Dr. Prieftley over mercury, a beautiful 

 white cloud was formed, and a diminution in the 

 bulk of the airs took place. The cloud having fub- 

 fided, was found to con fi ft of common fal ammoniac, 

 pr a union uf the volatile alkali with the marine acid. 

 Nitrous, air admitted to alkaline air, like wife occa- 



fioned 



