W. E. Ford — Optical Study of the Amphiboles. 193 



The fact that the iron content of an amphibole has a large 

 influence upon the optical characters was stated as long ago as 

 1871 by Tschermak* and has recently been emphasized by 

 Kreutz.f The results of the present study, as already given, 

 bear out his statement. 



Wiik;}; endeavored to show that the size of the extinction 

 angle, C/\C, increased as the percentages of A1 2 3 increased. 

 This theory has already been shown by others to be untenable 

 and the results of the present study point to the same conclu- 

 sion. 



Mineralogical Laboratory of the Sheffield Scientific School, 

 Yale University, New Haven, Conn., July 2, 1913. 



*Min. Mitt., p. 17, 1871. f Min. Mitt., xxvii, 250, 1908. 



JZs. Kr.,vii, 79, 1883. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Action of Aluminium Carbide upon Solutions of 

 Metallic Salts. — Hilpert and Ditmar have found that aluminium 

 carbide, which has the formula A1 4 C 3 and which reacts with 

 water and with acids giving methane, CH 4 , is capable of methylat- 

 ing certain metals when it acts upon solutions of their salts. For 

 instance, when aluminium carbide is placed in a hydrochloric 

 acid solution of mercuric chloride, mercuric methyl chloride, 

 HgCH 3 Cl, is formed, and when the solution is neutral or slightly 

 acid, mercury dimethyl, Hg(CH 3 ) 2 , is produced. In the same 

 manner bismuth trimethyl, Bi(CH 3 ) 3 , which is otherwise difficult 

 to obtain, can be synthesized. Tin salts also are methylated by 

 aluminium carbide, and in this case the tin-methyl compounds, 

 on account of their intense and characteristic odor, may be used 

 as a qualitative reaction for tin, for even as small a quantity as 

 0*1 mg. of stannous or stannic chloride in 2 ccm. of dilute hydro- 

 chloric acid, upon boiling with a small quantity of aluminium 

 carbide, gives a strong odor. Preliminary experiments have 

 shown that not only arsenic and antimony can thus be methy- 

 lated, but also other metals with which such compounds have not 

 been previously obtained. For example, there is formed in the 

 reaction between copper sulphate and aluminium carbide a com- 

 pound with a disagreeable odor resembling mercury methyl. The 

 exact mechanism of these interesting reactions is uncertain, and it 

 is remarkable that the authors have not been able to methylate 



