510 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



made by mixing together different kinds of ochre. Under 

 the name of Alexander blue, the ancients Egyptians as well 

 as Greeks and Romans used a pigment containing oxide of 

 copper, and also one containing cobalt. Fabrics were dyed 

 blue by means of pastel-wood (Isatis tinctoria). Yellow pig- 

 ments were principally derived from saffron and other native 

 plants. Vermilion, red ochres, and minium were known from 

 a remote antiquity, although the artificial preparation of ver- 

 milion was a secret possessed only by the Chinese. Kermes 

 was used in Egypt in the time of Moses. Among green paints 

 the ancients knew only certain green-colored compounds of 

 copper with the acetate of that metal. The celebrated Tyrian 

 purple was obtained from a mollusk known as the Janthina 

 prolongate a shell abundant in the Mediterranean and very 

 common near Narbonne, where Tyrian purple dye-works were 

 in operation at least six hundred years before Christ. 1G A, 

 January, 1 872, 1 1 1. 



DYEING ALPACA WITH IODINE GREEN. 



This is effected as follows : The material is first placed 

 moist in a bath of iodine green (a quarter of a pound of the 

 powder to ten pounds of the cloth), spirits of hartshorn 

 (about a quarter of a pound), a little sulphuric acid, and a 

 quarter of a pound of soda water-glass or silicate of soda. 

 They are to be kept in this a short time, and then drawn 

 quickly through a hot solution of tannin, brought back again 

 into the first bath, and then placed in a tolerably strong acid 

 bath. 13 C, November 1, 1871, 1390. 



NEW COLORIMETER. 



A new form of colorimeter is made by bringing two stout, 

 square, well-polished plates of glass in contact with each other 

 along one of the edges, the opposite edge being separated by 

 a piece of platinum wire, of determinate thickness, leaving a 

 very narrow wedge-shaped space between the two plates. 

 On the under side of the lower plate there is to be a gradua- 

 tion, which is to be examined through the upper plate after 

 the liquid to be tested is introduced between the two. To 

 test milk with this instrument, a few drops are to be intro- 

 duced in the wedge-shaped interval, and the scale observed 

 through it. The last graduation, still legible, furnishes a scale 



