On the Ammon'ture and Acid of Cobalt. 127 



the hair often fwells in fuch a manner that blood Iflues from 

 it when cut." 



Dr. Brera is of opinion, that this terrible difeafe is not to 

 be afcribed, as fome beUeve, to the dirtinefs of the people in 

 Poland. 



IX. On the Ammoniure of Cobalt, and an Acid contained in 

 the Cn-ey Oxyd of that Metal known under the Name of 

 Zaffar. ^ L. Brugn ATELLI *. 



X II E metallic ammoniures have for fome time pad en- 

 gaged my attention. Thefe compounds refult from a che- 

 mical combination of ammonia with metals. Hitherto they 

 have been little examined, that of copper excepted, notwiih- 

 ftanding their charaaeriltic properties, which diftinguifh them 

 from other bodies. The aumioniure, which firft became the 

 objea of my refearches, was that of cobalt f. The parti- 

 cularities which it prefented are as follows : — 



1. I had feveral times obferved that the precipitate, formed 

 by ammonia in a folution of the nitrat of cobalt, was re-dif- 

 folved in that alkali. I collected fome of it on a filter, 

 and wafted and dried it. On half an ounce of this precipitate, 

 which was of a dark colour, 1 poured two ounces of liquid 

 ammonia, flopped the bottle, and left it at reft. The tem- 

 perature of the atmofphere was 20" above zero of Reaumur. 

 At the end of twenty-four hours the alkali had aflumed a 

 dark-red colour :!:, and the precipitate was entirely diffolved. 

 I thought I had formed a pure ammoniure, but I endeavoured 

 to procure a larger quantity by other means. 



2. I tried to dillulvc fmalt or blue cobalt in canftic am- 

 monia, but without fuccefs, even when long digeftion was 



•'• From the Annates dc Cbitnie, No. 9!'. 



+ I have fince. examined the ammoniarcs of mercury, 7.inc, copper, 

 and arfcnic. 



+ Bergman had obrerved only that ammonia arfumed a red colour with 

 /ob:.lt. Cobaltum, fays he, a mccolo differt quod omnibus a/:idis et akuii 

 volatili folvatur colore rubra. This circumftancc has been noticed by all 

 chemifts without adding any thing to it. 



G g 2 employed ; 



