353 On some Comhinations of Platina. 



The two preceding expeiiments afford almost precisely 

 the same results; the metallic platina and sulphate of potac^h, 

 in both instances, weighed the same; and to diminish the 

 averaore loss, thev were mixed togetlier, and boiled if* 

 about a pint of distilled water : by this means all the sul- 

 phate of potash was dissolved, and the platina alone re- 

 mained. After the aqueous solution of sulphate ot potash 

 had been decanted ofl, and the grains of metal well washed 

 and heated to redness, they weighed 14-8 grains. 



Hence 10 grains of potash sulphate of platina afforded 

 grains."^ f 740 platina. 



Metallic platina.. 7*40 | j 9-0 oxygene. 



Oxveene Q-QO >°'' . < 1 1-5 diy sulphate of 



Sulphate of potash 1-15 | S''^'"^, j potash. 



Water 0-55 J L 5-5 water. 



And 100 grains previous to the expulsion of part of its 

 water by heal, contain 78*32 oxide of platina. 



10-84 sulphate of potash. 

 iO'84 water. 



100- 00 

 9. Of Soda Sulphate of Platina. 



This substance is procured in a similar martner as the 

 potash sulphate of platina, by treating sulphate of platinar 

 with a solution of pure soda, and boiling the materials for 

 a few minutes. The precipitate, after being well washed 

 with pure water, and dried for a considerable time at a tem- 

 perature not exceeding 212° Fahrenheit, exhibits properties 

 analogous to those of the potash sulphate of platina. 



Its colour is black or very dark brown. It is in small 

 hard lumps. It has a shining resinous lustre, similar tQ^ 

 that of the potash sulphate oT platina, but rather less di- 

 stinct. It is tasteless, and insoluble in water. The effects- 

 of the mineral acids and alkalies on it appear to be very 

 similar to those produced on the potash sulphate of platina. 

 Its general characters so closely resemble those of the potash: 

 sulphate of p!atina, that I have not observed a single pro- 

 perty which may be said distinctly to characterize the one 

 from the olhef. — Like that substance, it is decompounded 

 by the agency of heat, and this mode I adopted to ascertain 

 the proportions of its constituent parts. 



Analysis. 



Experiment 1. — IS-g grains of soda sulphate of platina, 

 after being dried for some days at a temperature varying 



from 



