204 ANNUAL OF SCIENTIFIC DISCOVERY. 



in Istria. The resin is brittle ; its color varies from, hyacinth red to 

 chestnut brown. The mineral exhibits a fatty gloss and is trans- 

 parent ; its fracture is plano-conchoidal ; its specific gravity is 

 1.025; it becomes highly electric when rubbed, and gives oft', on 

 bring gently heated and on being pulverized, an aromatic pleas- 

 ant odor; its melting-point varies from 168 to 180. When 

 fused the substance gives off a nasty, pungent smell, and when 

 the molten mass begins to boil, vapors are given off which, carried 

 into solutions of lead or copper salts, cause a black precipitate 

 therein. This resin was chemically investigated by Professor 

 Hlasiwetz, the result of whose research is as follows: The 

 substance is hardly soluble in alcohol or ether, but is perfectly 

 soluble in boiling benzol ; heated in a retort it melts, begins to 

 boil, then gives off sulphuretted hydrogen gas and yields an 

 oily distillate. The elementary analysis led to the following per- 

 centage results: carbon, 81.1, hydrogen, 11.2, sulphur, 4.7, 

 oxygen, 3.0; no ash. When treated with fusing caustic potash, 

 the resin is oxidized, but the products of this reaction did not 

 yield anything specific. The resin, appears to belong to the sub- 

 stances akin to copal; but the fact that it contains sulphur is 

 peculiar, since as yet no other fossil resin containing sulphur is 

 known except the tasmanite of Dr. Church (" Phil. Mag." xxxviii., 

 1864, p. 465). Tasmanite is, however, absolutely insoluble in. 

 benzol. Chemical News, from the Jahrbuch der K. K. Geologischen 

 Bdclisanstalt, No. 2, 1870. 



New Volumetric Method for tlie Estimation of Copper. This 

 method, proposed by Weil, is based upon the following facts : 

 (1.) That in the pressure of an excess of free chlorhydric 

 acid and at the temperature of boiling, the least trace of bi- 

 chloride of copper communicates a very marked yellowish-green 

 tint to the solution. The greater the excess of chlorhydric acid 

 the more intense the coloration : (2.) That at this temperature 

 protochloride of tin instantly reduces the bichloride of copper to 

 protochloride, which is colorless. The moment at which the re- 

 action is finished is indicated by the complete decoloration of the 

 liquid. When the liquor to be titrated contains iron as well as 

 copper, the amount of protochloride of tin indicates the sum of 

 the iron and copper. In this case the iron is titrated in a separate 

 portion of the assay in sulphuric acid solution with permanganate 

 of potassium after precipitation of the copper by means of zinc 

 and platinum. The solution of protochloride of tin is standard- 

 ized with pure copper and preserved from oxidation by a layer 

 of petroleum. Comptes Rendus, May 2, 1870, p. 997. 



Detection of Arsenic in Tartar Emetic. To as much tartar 

 emetic as can be held on the point of a good-sized knife, is added 

 twice as much pure protochloride of tin, and the mixture intro- 

 duced into a wide test-tube ; 4 or 5 c. c. of pure chlorhydric acid 

 (containing 25 per. cent real acid) are added; and subsequently 2 

 or 3 c. c. pure concentrated sulphuric acid. If the adding of the 

 sulphuric acid does not heat the contents of the tube sufficiently, 

 the mixture should be warmed over the lamp. If arsenic be 

 present the fluid becomes yellowish, then brown, and finally a 



