InteUi^enca and Miscellanies. 395 



'to 



in England, that a large quantity of perioduret of mercury is 

 sold in that country under the name of English vermilHon 

 which is employed principally ni the preparation of paper 

 hangings. Learning also that Iodine was used in printing 

 calico he analysed a specimen of the coloring material from 

 Glasgow, and succeeded in forming a compound which was 

 a perfect imitation of the English salts. The proportions 

 which he found to succeed best were the following. 



Hydriodate of potash •■ • - 65 



lodaie of potash - - - - 2 



loduret of mercury - - - 33 



100 



This salt appeared to have cost in England one hundred 

 francs the kilogramme (2lb. 3 oz.) but could be prepared in 

 France for thirty-six francs, reckoning the lodme to cost 

 forty francs. 



" It appears to me (observes this skilful chemist) that this 

 salt ought to be applied to the stufFbefore it is passed throuo^h 

 metallic solutions. Among the latter, those which give the 

 most beautiful colors are the solutions of lead and mercury. 

 This salt may be applied with advantage to stuffs by the aid 

 of a solution of starch which becomes a beautiful violet, (a 

 known effect of Iodine and starch.) The starch appears al- 

 so to contribute to fix the salt on the stuffs. 



There is another salt also much employed it is said in 

 Glasgow, in calico printing, which I ought also to mention, 

 because it appears not to be much used in France. This is 

 a triple acetate of lime and copper, prepared in the large 

 way by Ramsay, at Glasgovv, for the printers. This salt is of 

 a very beautiful blue. It crystalizes in straight prisms with 

 square bases. The summits of the prisms are often replaced 

 by facets, whence result prisms with six or eight planes ac- 

 cording to the extension which the secondary faces acquire. 



When this salt is decomposed by a fixed alkali, the oxide 

 of copper and lime are precipitated combined, because they 

 meet in the nascent state and in definite proportions. It is 

 certain that the precipitate turns green but little in the air 

 even in drying, and in its application, it is a kind of ash blue 

 which becomes fixed on the stuff. I call the attention of cot- 

 ton printers to this salt, which may furnish very beautiful 

 dyes, and which cannot become very expensive. — Bulletin 

 d^ encouragement., Sept. 1828. 



