324 Dr. Thomas Thomson on [May 



weak solution of chloride of lime (bleaching powder,) or of 

 bichromate of potash. Should such a process be incom- 

 patible with the other colours, the cloth is merely exposed 

 to the air for a considerable time, by which the blue be- 

 comes almost as deep as when chloride of lime is employed. 



4. Steam-Green. — This colour is, in fact, v a combination 

 of the preceding, with a yellow colour, produced by a de- 

 coction of Persian berries, and fixed on the cloth by alum. 

 The precipitate of potash is dissolved in water, and this 

 liquid is mixed with a decoction of Persian berries and 

 alum. These substances have no sensible action on each 

 other while cold. But on the application of steam after 

 printing, the acid of the alum becomes united with the 

 potash, while the alumina combines with the yellow colour- 

 ing matter of the Persian berries, and fixes it on the cloth. 

 At the same time the heat causes the deposition of the white 

 Prussian-blue, which gradually assumes a blue colour by 

 exposure to the air. The blue and yellow colours united 

 are well known to produce a green. 



5. Annatto Orange. — Annatto is dissolved in potash or 

 soda, and printed on the cloth. This constitutes the whole 

 process. 



6. Chrome Yellow upon Turkey- Red. 



This is produced by a modification of the patent process 

 described in a former part of this article. Tartaric acid 

 and nitrate of lead are dissolved together in water, which 

 is thickened with gum, and printed on those parts of the 

 Turkey-red cloth that are to become yellow. When the 

 cloth is passed through a solution of bleaching powder, 



