KICKEL AND COBALT. HG^ 



porated till a pellicle was formed, and, after being filtered, 

 was left near a ftove, that it might cool flowly and cryfbllize. 

 At the end of 4-8 hours, the greateft pari of the fult was cry- Pioduces fine 

 fiaUized in beautiful tetrahedral rhomboidal pyramids, (liort, hidiahhoniboill 

 and of a yellow green, of which tlie lateral faces formed an al pyramids. 

 gles of 1 15 and of 65 degrees, often with one extremity 

 truncated, and always with an angle of 132 degrees towards 

 its terminating face. This refult proves that this fait forms 

 more readily into regular cryfials by cooling than by flow eva- 

 poration. All the cryfials were then coilefled, watlied with 

 water, and again difTolved, and the nickel feparated by boiU The cryMs d;f- 

 ing the folution with potafh till the ammonia was difen-^ ^kpl lepaiatci 

 gaged. as before. 



4. As well to free this oxide from carbonic acid as to judge The oxide ob- 

 if it had been purified from cobalt, it was difTolved in "ilf't^ innLic'acid'and 

 acid and treated with pure ammonia in the fame manner as treated with am- 

 has been defcribed. The liquor of a fine blue colour, (and .'^'^ j '/^'/'f Jj^, 

 from which a refidue of five grain*;, which feemed to be an folved depofits a 

 oxide of cobalt, had been feparated by filtration), was eva- S'"" o^'Qe. 

 porated to drynefs. After another folution then made, it de- 

 pofited an oxide of a beautiful brij^^ht green, which, after 

 being waflied and dried, weighed half an ounce. The liquor, The filtered li, 

 which pafTed the filter, was analyfed by pure carbonate o^pou/h 170 "L 

 potaQi at the heat of boiling water, which then produced 1 70 oxide of nkkd. 

 grains of oxide of nickel, of a pale green, united to carbo- 

 nic acid ; a little of it was ditfolved in muriatic acid, and fome 

 of the folution fpread upon paper. On heating it afterwards, 

 the tint became yellow, and inclined but very little to a green. 

 But the oxide of nickel, which feparated fpontaneoufly during 

 the evaporation, was dilTolved in difengaging much oximuri- 

 atic acid; fpread on paper, it exhibited tlie colour, when 

 heated, of a fympatheficink of cobalt highly faturated ; from 

 whence it follows that it was more rich in cobalt than that pro- Which contains 



J ^ , ... Jefs cobalt than 



cured from the precipitation. tlie fpontaneous 



The oxides colleded in thofe two ways, difTolved in nitric precipitate. 

 and fulphuric acids, after becoming grey, (which the author ^^1^^^°^'^^"^.;^"" 

 fuppofed to be occafioned by the nickel diffolving firft, and and fulphuiic 

 at leaft the greateft part of the cobalt remaining to the lafl,^'^' *' 

 but which opinion was not confirmed by other experiments 

 made on this fuhjed.) Thefe oxides made lightly red in the Give out mtrmt 

 ifire, changed their colour to a dark grey, and then, as well as J^ fuiphurlc '" 



on acid. 



