362 Scientific Intelligence. 



phorus and the previously known modifications is its high density, 

 which is 2*691, while that of white phosphorus is 1*83, and that 

 of red phosphorus varies according to the method of preparation 

 from 2-05 to a maximum of 2*34 for Hittorf's "metallic " crystal- 

 lized red phosphorus. The black phosphorus is ignited with 

 difficulty, is stable in the air, and while almost opaque, shows a 

 translucence of an olive-brown color when very minute particles 

 are observed under the microscope. These minute particles show 

 action upon polarized light, so that it is evident that the sub- 

 stance is crystalline. The black phosphorus is remarkable in 

 possessing a fair amount of electrical conductivity. — Jour. Amer. 

 Chem. Soc, xxxvi, 1344. h. l. w. 



3. The Detection of Cyanides in the Presence of Ferrocyanides, 

 Ferricyanides and Thiocyanates. — For this qualitative test O. C. 

 Barnebey uses the well-known reaction of copper sulphide with 

 cyanides. The reagent is a dilute ammoniacal solution of copper 

 sulphate. To a little of this liquid a little hydrogen sulphide is 

 added, which gives a black precipitate of copper sulphide. 

 Upon adding this black liquid to an ammoniacal solution of the 

 substance to be tested, or making a vice versa addition, in the 

 presence of a cyanide the black color of the copper sulphide is 

 discharged. The other cyanogen derivatives do not have this 

 effect, and by using a copper solution of known strength and vol- 

 ume an idea of the amount of cyanide present can be formed. 

 The reaction was found to be capable of detecting 0*5 mg. of 

 HCN" in the presence, in 50 cc , of 2 g. either of potassium ferro- 

 cyanide, ferricyanide or thiocyanate, and in the presence of small 

 quantities of these substances the test is reliable down to # 1 mg. 

 of HCN. — Jour. Amer. Chem. Soc, xxxvi, 1092. h. l. w. 



4. Colorimetric Determinations. — C. Huttner recommends 

 the use of the well-known colors produced by the chlorides of 

 cobalt, nickel, iron, and copper in solutions of fuming hydro- 

 chloric acid for the quantitative determination of these metals, 

 particularly when they are present in small amounts. He uses 

 solutions of known strength for comparison and states that the 

 error in matching the colors is usually not more than one- 

 twentieth of the whole amount, so that the method may be 

 applied without serious error in cases where the metal amounts 

 to several units per cent. For minute amounts, particularly of 

 iron and of copper, the method is exceedingly accurate. It is 

 important that the solutions compared, especially in the cases of 

 iron and copper, should be made up of hydrochloric acid of the 

 same strength, since the colors vary greatly with the strength of 

 the acid. — Zeitschr. anorgan. Chem., lxxxvi, 341. n. l. w. 



5. The Origin of the Cyanogen Bands. — In the aniline and 

 soda factories of Germany nitrogen is obtained from air by the 

 aid of alternating current arc lights, some of which attain as great 

 a length as 8 meters. The flame is made stable by introducing 

 the gas into the main tube through a smaller tangential tube. In 

 this way an ascending, helical vortex of gas is maintained and 



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