24 Mr. kir wan’s Experiments and Obfervations on 
catcd in a vaporous date. ioo grs. of horn filver contain 75 
or illver, nearly 1 8 of acid, and 7 of water. 
Gold in aqua regia. 
I made feveral experiments with aqua regia, in which the 
nitrous and marine acids were mixed in different proportions, 
and found that to fucceed bed, in which the quantity of real 
'marine acid was to that of the nitrous as 3 to 1, and both as 
concentrated as pofiible ; though if both be very concentrated, 
it is hard to mix them fo as to prevent a great quantity from 
efcaping, as they effervefce very violently fome time after mix- 
ture, 100 grs. of gold require 246 grs. real acid for their folu- 
tion, the two acids being in the above mentioned proportion. 
The fpecifc gravity of the nitrous acid I ufed was 1,465, and 
that of the marine 1,178. The folution is better promoted by 
allowing it fufficient time than by applying heat. The heat I 
uled did not exceed 90 or ioo°. Very little air is produced, and 
the folution is very flow. Aqua regia made with common fait 
or fal ammoniac and fpirit of nitre is much lefs aqueous, than 
that refulting from an immediate combination of both acids ; 
and hence is the fitted for the produdtion of crydals of gold. 
Gold is alfo foluble in the dephlogidicated marine acid, but 
in very fmall quantity, unlefs this acid be in a vaporous date, 
for in a liquid date it is too aqueous. In vitriolic and nitrous 
acids it is alfo infoluble ; but the calces of gold are eafily folu- 
ble in the marine acid, very flightly in the nitrous, and icarce 
at all in the vitriolic. Gold in its metallic date may he diffufed 
■through, but not didblved, by the concentrated nitrous acid. 
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