By boiling this varnish with dilute nitric acid vapours of acrolein are given off, and the substance gradually becomes a solid non-adhesive mass the same as the ultimate oxidation product of both raw and boiled oil.
In varnish manufacture; it is also used for a fuel; a purer product is extensively used in the colour and fine chemical industries.
Among the other important manufactures in 1905 were: chemicals, valued at $3,964,726; slaughtering and meat packing, $2,933,877; varnish, $2,893,305; stamped ware, $2,689,766; enamelled goods, $2,361,350; boots and shoes, $2,382,051; reduction of gold and silver, not from ore, $2,361,350; corsets, $2,081,761; paints, $1,812,463; silverware and silver-smithing, $1,780,906; tobacco, cigars and cigarettes, $1,742,862; hardware, $ 1, 6 16, 755; buttons, $1,281,528, and saddlery hardware, $1,151,789.
The " ni-in " (also known as " axe ") is a small scale insect belonging to the genus Coccus, found in Yucatan, Oaxaca, Vera Cruz, Michoacan and other southern states, where it inhabits the spondia trees and produces a greasy substance called " ni-inea," which is much used by the natives as a varnish, especially for domestic utensils, as it resists fire as well as water.
It is allied to copal in its nature and appearance, and is much used by varnish-makers.