134 ESSAY VI. 



was mixed with charcoal powder and distilled. An ebullition 

 took place, some regulus of arsenic rose into the neck of the 

 retort, and the ' antimony was reduced, (c) Butter of 

 antimony was not precipitated by the acid of arsenic, but 

 readily by the neutral arsenical salts. The solutions of glass 

 of antimony in vinegar and cream of tartar are precipitated 

 by the acid of arsenic. 



SECTION XXXIII. UPON COBALT. 



(a) The acid of arsenic digested with cobalt assumed 

 a rose colour, but a great deal of the cobalt remained un- 

 dissolved. (6) I put the whole mass into a retort, and 

 abstracted it to dryness ; then, on increasing the heat, it 

 entered into fusion, and a little arsenic was sublimed. After 

 the mass was grown cool, it had a semitransparent violet 

 colour. I then poured water upon it, and put it into hot 

 sand; the acid was dissolved, the violet colour disappeared, 

 and the solution turned dark red. The bottom of the retort 

 was blue, and no menstruum was capable of taking this 

 colour out of the glass, (c) Neither the solutions of cobalt 

 in mineral acids nor vinegar are precipitated by the acid of 

 arsenic ; but the arsenical neutral salts produce a precipita- 

 tion of a rose colour. This precipitate is difficult of fusion 

 in the crucible, and has the appearance of a dark blue scoria. 



SECTION XXXIV. UPON NICKEL. 



(a) The acid of arsenic digested with nickel assumes a 

 green colour ; a quantity of green powder mixed with arsenic 

 is precipitated. The arsenic may be separated from it by a 

 gentle heat. (&) One part of nickel was mixed with two 

 parts of dry acid of arsenic and distilled by a strong fire. 

 The mass melted with an appearance of inflammation, and 



