M. TECHNOLOGY. 573 



they are about the size of a grain of rice ; but after the wax 

 is produced, the accumulation is as large as a hen's egg. The 

 insect commences to secrete the viscous substance in the 

 s^^ring, this taking the form of a silky down, which thickens 

 and hardens. In August or September the balls hang like 

 grapes, which are gathered by detaching them with the fin- 

 gers, and after being dried in the sun they are purified and 

 refined. This wax is in general use in China and Japan, 

 where large tracts of land are planted with the trees referred 

 to, upon which the insects are reared. The insect is propa- 

 gated by means of its eggs, which are collected in clusters in 

 the shells of the balls. As met with in commerce, the peh- 

 lah wax is nearly pure, and melts at 190 Fahr. It is sold 

 in cakes of a circular form, and of different sizes. It dissolves 

 easily in naphtha, and contains eighty-two per cent, of car- 

 bon, fourteen of hydrogen, and four of oxygen. It is used 

 like bees-wax in making candles, and for other similar pur- 

 poses, where its high melting temperature is an advantage. 

 The light of these candles is of great brilliancy, and, if a little 

 oil be mixed with the wax, they do not gutter. It has been 

 known in Europe about twenty years ; but, so far, its impor- 

 tation has not been as great as the value of the material would 

 seem to warrant. 17 A, 3fay 1, 1872, 262. 



DETECTION OF ADULTERATIONS OF MADDEE. 



A simple method, quoted from Pernod, is given in Iroii^ 

 for detecting the more probable adulterations of madder. 

 These he divides into two classes : those which give colored 

 compounds with oxide of tin, etc., such as logwood, peach- 

 wood, burwood, etc. ; and those which contain tannin, with 

 little or no coloring matter, such as oak-bark, extract of 

 chestnut, etc. These latter substances produce a black or 

 brown color with solutions of iron. To detect adulterations 

 of the first class, take a piece of white paper of four inches 

 square, dip it into a solution of tin crystals, lay it on a white 

 earthenware plate, and sprinkle a little of the finely pow- 

 dered sample ujDon it. If logwood be present, purple spots 

 Avill ajipear in about half an hour. Peach and barwood will 

 be betrayed by red spots, and fustic by yellow ; while pure 

 madder gives merely a faint yellow color. A piece of paper, 



