OJi PREPARATIONS OF COLD. 24p 



There is some difficulty in obtaining these preparations DifficuUtoob- 



constantlv in the same state; and one of the principal ob- '/'" ^*^®^® ""*' 



. . lorin. 



jects in the art of physic being precisely this constancy in 



the nature of rnedicines, it appeared to me of some utility 



to examine these preparations, and to describe with accuracy 



the processes best adapted for obtaining thenj. 



3^CT. J, Of the quality and qtimitity of nitromuriatic ncld 

 most suitable for dissolving Gold. 



It was formerly the practice, to compose nitromuriatic Nitromuriatk 

 acid of tw6 parts of nitric and one of muriatic, by weight. ^.^'''' ^''' '^"^ 

 But on considering, that gold requires only a very small trie, dissolve 1 

 portion of oxigen for its solution, and that the nitric acid in P-o'gold. 

 the process in question answers this purpose alone, I con- i 

 eluded, that the same purpose would be obtained, if an 

 iaqua regia were composed of the two acids in opposite pro- 

 portions to those hitherto directed. In fact, three parts of 

 nitromuriatic acid thus made were sufficient to dissolve one 

 part of tine gold, while at least four mude in the old wajr 

 were required, 



iV proof of the small quantity of oxigen, that combines But little o^i- 

 with gold at the moment of its solution may be found in the wi'thgoUl."^ 

 very small quantity of nitrous gas evolved: beside which 

 there is reason to presume, that some portion of this gas js 

 prpduced by the action thi^t takes plac6 between the two 

 acids, since some oximuriatic acid is evolved likewise 



The solution of gold, when duly evnporaled, crystallizes The solution 

 in yellow prisrns, the figure of which, I beiievt, has never ^^^* ^ ^"^* 

 yet been ascertained \vith precision. 



The eviiporation of the solution must be conducted with bnt is partly- 

 great caution, otherwise part of the salt will be decomposed, aecomposed 

 ** _ ..' . without great 



3nd the gold will reappear in its natural state, in the form care. 



of small scales. 



The solution of muriate of gold comports itself with the Action of 

 fixed alkalis in a riianner different from that of other metals ; ^•l^a''**^" •*' 

 most of which, it is welJ known, ar^ completely precipitated 

 hy tiiem in the state of oxide. 



potash, soda, barytes, and lime, do not render the solu- Do net preci- 

 liop of gold in the least turbid, at common temperatures. P"^^« 'N 

 Jt only acquires a very deep red colour with potash and 



soda 



