J40 Experiments on Plathia, 



portion of the liquor to efcape. If the concentration has 

 not come to that point, and if the rcfidiuun prefcnts only a 

 thick fuhftance like honey, it mull be again placed over the 

 fire. But if it has been carried too far; ihat is to fay, if the 

 feparation of the liquid part cannot be effecU-d, you mu(t 

 then add to the mafs, which we here fuppofe to be lour or 

 five pounds, fome Ipoonfuls of water, and redilfolve it by the 

 help of heat and ebullition. This method, which is very 

 eafy for thofe acquainted with the practice of the laboratory, 

 is the fame as that employed for refining fugar, and fepa- 

 rating from it the niolallcs. 



Aiter having lurmounted this obllaclc, the reft becomes 

 eafy. Nothing then is necefTary but to add a quantity of 

 water nearly equal to the volume of the mnriates that have 

 thus been fcparated ; to expofe the whole to heat ; to futfer 

 the retort to cool in the furnace ; and to proceed to two or 

 three fucccfiive diftillalions, to feparate the cryftals of the 

 muriate of platina. 



This meihod has a double objed — the cr\'ftallization of 

 the muriiue, and its purification. It is evident, and cannot 

 be douljied, tliat, by repeating this procefs a fufficient 

 number .f titncs, platina may be as completely purified 

 as by any cf the other means hitherto known. But while 

 we admu ;iil the utility of this method, we muft allow that 

 it is tedious and troublefome, both in regard to the cryftai- 

 lization of the muriate, and its purification. The others 

 therefore, in our opinion, ought to be preferred; for, to 

 obtain liiC cryftals with the greateft eafe, it will be fufficient 

 to concentrate a folution of platina purified by a procefs 

 wliich we ftiall fp'.ak of hereafter. If anv one, however, 

 wiftics to carry this method of purification to the hioheft 

 degree, he may be certain of having attained to it by making 

 the follow ing experiment : 



Djffol ve, in a certain quantity of water,, a little of this mu- 

 riate, and try it with ammonia. If the common yellow pre- 

 cipitate of the red oxide of iron be obtained, there ftili re- 

 mains fome muriate of the latter combined with the platina ; 

 but the muriate of platina is pure if no pveoipiiate manifefls 

 itfelf. 



It is of importance that the folution (liould be well di- 

 kited, otherwil'e the ammonia would form with the platina 

 that kind of faline precipitate which is produced by the mu- 

 riate of ammonia. 



At the moment of their concentration thefe folutions of 

 platina experience a bubbling, which would endanger the 

 retort if the p( rfon who eondu6ts the operation perfifted in 



continuiiKr 



