1,8 Mr. kirwan’s Experiments and Obfervations on 
of nitrous air ; and by diftilling the folution a ftill greater 
quantity may be obtained, which wasabforbed by the folution. 
No inflammable air is obtained from folutions of iron or 
any other metallic fubftance in the nitrous acid, becaufe this 
acid has lefs affinity to water, and more to phlogifton, than 
the vitriolic acid, and alfo contains much lefs fire than either 
r he vitriolic or marine acids, as will be feen in the lequel, and 
therefore unites to phlogifton inftead of barely expelling it. 
And hence it is, that the vitriolic acid, though united with 30 
times its weight of water, will ftill vifibly aft 011 iron, and fepa- 
rate inflammable air in the temperature of 55° ; whereas nitrous 
acid, diluted with 15 times its weight of water, will have no 
vilible effeft on iron in that temperature. 
The calces of iron, if not too much dephlogifticated, are 
alfo foluble, though difficultly, in the nitrous acid. 
Iron in the marine acid. 
100 grs. of iron require 215 of real marine acid for their 
folution* The proportion of acid to that of water in the fpirit 
of fait I ufed w 7 as as 1 to 4. When it is as 1 to 4, it effervelces 
too violently. Heat is rather prejudicial, as it volatilifes the acid. 
No marine air flies off, and the quantity of inflammable air is 
juft the fame as if dilute vitriolic acid were ufed. 
The calces of iron are alfo foluble in marine acid. They 
may be diftinguifhed from genuine iron in this, that their 
colour, when precipitated by fixed alkalies, is reddij}.\ whereas 
the precipitate of genuine iron is greenijh. 
Copper in the vitriolic acid. 
1 00 grs. of copper require nearly 183 grs. real vitriolic acid 
for their folution. The proportion of acid to that of water 
4 being 
