Practical Magazine 14, 1876
(Chemistry applied to the Arts, Manufactures, &c.
Dyeing, Calico Printing, Bleaching, Tanning, and Allied Subjects.)
To ascertain whether olive oil is pure and suitable for dyeing Turkey red, M. KOPP adopts the following process: —
Into an experimenting glass are poured ten volumes of the oil to be tested and one volume of ordinary nitric acid, to which are added some pieces of turnery shavings or red copper wire. The nitrogen forms with the nitric acid nitrous acid, the bubbles of which pass over the layer of oil floating on the top. The oil and the acids are immediately mixed as much as possible with a glass stick. In about five minutes the two liquids separate, and they are again mixed by shaking. The glass is then left at rest in a cool place with a temperature of 12° to 15° C. (54° to 59° Fah.), and separation again takes place, the nitric acid being of a blue colour, in consequence of the formation of nitrate of copper (NO3)2 Cu.
The oil then collects into a mass with a rapidity proportioned to its purity, the elaidine being not only firm but perfectly white. When olive oil is mixed with other oils the formation of elaidine is slower, and the substance obtained is more or less brown or yellow.
- Technologiste, from Deutsch. Chem. Gesellschaft, 1875.
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