CHEMICAL SCIENCE. 211 



Those who are not familiar with chemical pursuits, and who may wish to 

 test specimens of green material for themselves, may easily do so in the 

 following manner. A piece of the size of the top of a tumbler is taken, 

 placed in a glass, covered with strong ammonia, and left to stand for a few 

 hours. As the green arsenical pigments always contain copper, which im- 

 parts a bine color to ammonia, the absence of such a coloration may be 

 taken as a probable proof of the absence of Scheele's or Schweinfurth green. 

 If the blue coloration makes itself evident, the liquid is to be poured carefully 

 off, so as to be quite clear, and a fragment of lunar caustic, previously 

 wiped perfectly clean with a wet cloth, is to be dropped into it. If the 

 caustic turns yellow, and diffuses a slight yellow cloudiness, either perma- 

 nent or soon disappearing, arsenic is present. 



T'.L Chcvallier has recently published a book devoted expressly to this 

 subject, the extension of which has attracted much attention, particularly 

 since arsenical dyes have been used for material for ladies' dresses, and his 

 work has been already translated into German. It is asserted that the 

 French government is taking active steps to put a stop to this dishonorable 

 trade, and we hope that legislative enactments to restrain it may be put in 

 force in the United States. 



NEW METALLIC CEMENTS. 



M. Greshiem states that an alloy of copper and mercury, prepared as fol- 

 lows, is capable of attaching itself firmly to the surfaces of metal, glass, and 

 porcelain. From twenty to thirty parts" of finely divided copper, obtained by 

 the reduction of oxide of copper with hydrogen, or by precipitation from 

 solution of its sulphate with zinc, are made into a paste with oil of vitriol 

 and seventy parts of mercury added, the whole being well triturated. When 

 the amalgamation is complete, the acid is removed by washing with boiling 

 water, and the compound allowed to cool. In ten or twelve hours it becomes 

 sufficiently hard to receive a brilliant polish, and to scratch the surface of tin 

 or gold. By heat it assumes the consistence of wax, and does not contract 

 on cooling. 



Neio Cement for filling Decayed Teeth, and for other purposes. M. Feich- 

 tinger communicates the following receipt to the Repertoire de Pharmarie : 

 Take of powdered glass one part, oxide of zinc three parts, and mix them 

 intimately. The two substances must be in impalpable powder, and the latter 

 must be free from carbonate of zinc. Then take of a solution of chloride 

 of zinc (density 1.5 to 1.0) fifty parts, borax one part. Dissolve the borax 

 in a little hot water, and pour it into the chloride of zinc; borate of zinc 

 is precipitated, which disappears on agitating the mixture. To make the 

 cement, mix the powder with enough of the solution to form a stiff paste. 

 Only so much as may be wanted at the time should be mixed, as the com- 

 pound quickly hardens. In the course of a little time it becomes as hard as 

 marble, and remains so, even after prolonged contact with water. If the 

 ingredients are pure, the cement is perfectly white. Chemical News. 



PROCESS FOR SILVERING ANIMAL, VEGETABLE, AND MINERAL 



SUBSTANCES. 



Liq'tor No. 1. Take two parts, by weight, of caustic lime, five of sugar 

 of miik or grape sugar, two of gallic acid, and make of them a mixture hi 



