CHEMICAL SCIENCE. 211 



ton market by Mr. Henry Brown, of the Cambridge Laboratory, prob- 

 ably indicates the average purity of this article as ordinarily sold. As 

 pure sulphide of mercury upon the application of heat volatilizes read- 

 ily, the fact of a residue remaining after igniting a sample of vermil- 

 ion upon platinum is a proof of the presence of impurities. This test 

 showed six out of ten varieties of vermilion submitted to analysis to be 

 adulterated. The qualitative examination of the residues indicated the 

 presence of carbonate of magnesia, sulphate of lime, chromate of lead, 

 and red oxide of lead. Ammonia salts, or other salts of mercury, which 

 are also volatile, are too expensive for the purpose of adulteration, if 

 they admit of being so incorporated with a superior quantity of genuine 

 vermilion as to escape recognition. None of them were found upon 

 examination. 



The following abstract exhibits the result of the analyses : Trieste 

 vermilion, Sample No. 1, entirely volatilized upon platinum, Hg S 

 (sulphide of mercury) = 100, pure. No. 2, do. No. 3, HgS = 

 85.06, MgO, CO 2 (carbonate of magnesia) = 14.94. No. 4, Hg S 

 = 73.43, Mg O, C O 2 = 26.57. No. 5, pure. Sample No. 6, French 

 vermilion, pure. No. 7, do., Hg S = 64.13, CaO,SO 3 (sulphate of 

 lime) =35. 87. Sample No. 8, Chinese vermilion, HgS = 37.64, 

 PbO, CrQ3 (chromate of lead) = 62.36. No. 9, do., Hg 8 = 37.88. 

 PbO,Cr0 3 = 48.12. Sample No. 10, American vermilion, so called. 

 This consisted wholly of red lead, without a particle of mercury con- 

 tained in it. 



In color, Nos. 9 and 10 were a deep red, bordering on purple ; 

 No. 8 was lighter. Nos. 1 and 6 were lighter than Nos. 2, 3, and 

 5; and Nos. 2, 3, 4, 5, and 7 could not be distinguished from each 

 other, so perfect was the incorporation of the white with the red. 

 Editors. 



NEW COLORING MATERIALS. 



IN the Journal de Pharmacie et de Chimie for January, M. Garot 

 communicates some results respecting the red coloring substance of 

 exotic and indigenous rhubarb, and its application to the arts. He 

 finds that by treating one part of rhubarb with four parts of nitric acid, 

 the residue which is not acted upon by the acid consists of a peculiar 

 substance, amounting in the indigenous rhubarbs to from 8 to 10 per 

 cent., and in the exotic rhubarbs to from 15 to 20 per cent. This 

 substance, which in the indigenous varieties is yellow and in the exotic 

 red, has been called crythrose, and forms with the alkalies red or pur- 

 ple compounds susceptible of application to the arts and to pharmacy. 

 The erythrosate of potash possesses a tinctorial power (in alcohol or 

 any other non-acid liquor) six times greater than cochineal, and the 

 red obtained is brighter and as stable. The erythrosate of ammonia, 

 after a dissipation of the excess of alkali, possesses the same proper- 

 ties as the potash compound, and its tinctorial power is at least four 

 times greater. It may be employed as a red ink with advantage, 

 and may be also used profitably in imparting a rose color to soaps. 

 By modifying the mordants, the erythrose imparts to silk and wool 



