I 



Separation of Gold and Silver from the laser Metals. 1 25 



6. Dutch madder, two ounces; alum, one ounce; fer- 

 mented two days, and then treated bv Process i'. 

 7- Produce of Process \, ground in gum by Mr. Newman. 

 8. Produce of Process 1, ground in oil by Mr. Newman^ 

 S — 1. Smyrna n)adder, by Process 1. 



S — 2. Ditto Process 2. 



S — 3. Ditto Process 3. 



S — 4. Ditto Process 4. 



Certificates accompanied the foregoing description, from 

 Mr. Cotnian and Mr. Munn, testifying the merits of sir 

 H. Engklield's madder lakes, as water-colours ; and also 

 from iViessrs. West, Trumbull, Opie, Turner, Daniel, and 

 Hoppner^ speaking greatly in its favour, where it has beeu 

 tried in oil-colours. 



XIX. Anew Process for separating Gold and Silver from 



the baser .MetaL *. 



XJLitherto this process has always been, as far as I have 

 understood it, attended witli considerable difficulty in the 

 execution ; but, by that u hieh I am about to describe, is 

 done with exact certauity. It was discovered and commu- 

 jiicated to me by a gentleman in this neighbourhood. The 

 process consists in mixing not less than two parts of pow- 

 dered manganese with the impure or compound metal, 

 which should be previously flattened or spread out so as to 

 expose as large a surhtce as possible, and broken or cut 

 into small pieces for the convenience of putting the whole 

 into a crucible, which then is to be kept in a sufficient heat 

 for a short tinje. On removing the whole from the fire, and 

 allowing it to cool, the mixture is found to be converted into 

 a brownish powder, which powder or oxide is then to be 

 mixed with an equal juoportion of powdered glass, and 

 then submitted in a crucible to a sufficient heat, so as to 

 fuse the whole ; when tl'.e perfect metals are found at the 

 button: in a state of extreme purity; a circumstance of no 

 small importance to the artist and the chemist ; the latter 

 of whom will find no difficulty in separating the one from 

 the other with so little trouble compared with the usual 

 processes, that I have no doubt it will always be practised 

 m preference to the cupel. 



• Extracted from a Comniuiiic.ition by Dr. William Dvce, of Aber- 

 deen, inserted in the twcnty-stcoacl voIuniL of the Transactions of the 

 Society of Arts, &:c. ^ 



1 XX. Twenty' 



