184 Miscellaneous Intelligence. 



and copper 25, did not melt, gave a black oxide ; if the heat 

 be much elevated, the underpart of the oxide is white, and 

 is oxide of tin ; the upper is black, and comes from the copper. 

 The cupel is made of a rose colour. If the tin be impure from 

 iron, the oxide produced by it is marked with spots of a rust 

 colour. — Annates de Chimie, xii. p. 342. 



8. New Yellow Dye, for Wool, Silk, Cotton, Flax, ^c— M. Bra- 

 connot has lately applied realgar, or the sulphuret of arsenic, in 

 the manner of a dye to various materials, and from the success 

 he has met with, has no doubt it will become valuable to dyers. 

 The dye-stuft' is made by dissolving sulphuret of arsenic in 

 ammonia, but it requires certain precautions to succeed in do- 

 ing this : 1 part of sulphur, 2 parts of the white oxide of arse- 

 nic, and 5 parts of common pearl-ash, are to be fused in a 

 crucible, at a heat a little below redness ; a yellow mass results, 

 which is to be dissolved in hot water, and filtered. The filtered 

 solution, diluted with water, is to be treated with weak sulphuric 

 acid, and will give a very fine yellow precipitate. When wash- 

 ed, it dissolves with great facility in ammonia, forming a solu- 

 tion at first yellow, but becoming colourless by the addition of 

 more ammonia. The wool, silk, cotton, or linen is to be dipped 

 in this solution, more or less diluted, according to the colour 

 required, care being taken that no metallic vessels be used. On 

 taking them out again they are at first colourless, but as the 

 ammonia evaporates become yellow. They are to be exposed 

 to free access of air on all sides, and then washed and dried. 

 Wool should be left in the liquor until perfectly impregnated 

 with it, and on being withdrawn should be only slightly wrung, 

 or even not at all. Silk, cotton, and flax, merely require immer- 

 sion, and should have the excess of fluid wrung from them. 



This dyeing material has the power of giving all shades of 

 yellow, and is very permanent in the air : alkalies, and conse- 

 quently soap, injure it, but for taffeta, velvet, and other manu- 

 factures of that kind, it offers many advantages, — Annales de 

 Chimie, xii. p. 398. 



