M. TECHNOLOGY. 553 



sometimes takes place, and alumina hydrate is deposited in 

 the fibre of the material, this decomposition evidently hav- 

 ing been caused by the fibre of the woolen itself. 21 A^ Feb- 

 ruary, 1873,206. 



AN EBONY STAIN FOK WOOD. 



Apple, pear, and walnut wood, especially of fine grain, give 

 perfect imitations of ebony under the following treatment : 

 Boil in a glazed vessel, with water, four ounces of gall-nuts, 

 one ounce of logwood chips, half an ounce of vitriol, and half 

 an ounce of crystallized verdigris ; filter while warm, and 

 brush the wood with the hot solution a number of times. The 

 wood, thus stained black, is then to be coated two or three 

 times (being allowed to dry completely after each coating) 

 with a solution of one ounce of pure iron filings in a quart of 

 good wine vinegar. This is to be prepared hot, and allowed 

 to cool before use. 16 C, YL, 6 and Y, 104. 



SPECKS IN COCHINEAL DYES. 



It has Ion Of been noticed that fabrics colored with cochi- 

 neal are apt to exhibit black specks, which have been as- 

 cribed to the presence of iron. According to Guignet, how- 

 ever, these are due to the formation of a carminMe of lime, 

 which occurs in the form of black powder, insoluble in water. 

 This salt, of a red color, is soluble in acetic acid, without de- 

 composition ; and appears, on the drying of the solution, as 

 a black residuum. 3 C, November 25, 1872, 1152. 



EXTRACTION OF EAPE-SEED OIL BY BISULPHIDE OF CARBON. 



The removal of the oil from rape seed by means of bisul- 

 phide of carbon, according to Fischer, of Riesa, depends ma- 

 terially on several conditions to produce satisfactory results. 

 If the seeds are not properly crushed, the bisulphide can not 

 act ; and, if powdered, they stop up the tubes, stop-cocks, etc., 

 of the apparatus. Old seeds require more power in crush- 

 ing than fresh ones, and in all cases it is advantageous to em- 

 ploy heavy rollers. The extraction is most complete from 

 dry, fresh seeds ; less so from moist, unripe, or very old seeds. 

 According as the time employed in extracting varies from 

 one to ten hours, the amount left in the meal may vary from 

 one to three j^er cent. Temj^erature also demands attention, 



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