ABSTRACTS 



Authors of scientific papers are requested to see that abstracts, preferably 

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 this issue. 



PHYSICS. — The illumination from a radiating disk. Paul D. Foote. 

 Bureau of Standards Scientific Paper No. 263, pp. 583-586. 1916. 

 A knowledge of the illumination from a radiating disk is of practical 

 value to engineers, but certain solutions of this problem which have 

 appeared in technical journals have been in error. In this paper is given 

 the correct expression for the illumination produced by a diffusely and 

 uniformly radiating circular disk, at any point on any surface parallel 

 to the disk. P. D. F. 



PHYSICS. — Inclusions in the silver voltameter deposits. G. W. Vinal 

 and W. M. Bovard. Bureau of Standards Scientific Paper No. 

 271, pp. 147-172. 1916. 



For the purpose of determining the absolute value of the electrochemi- 

 cal equivalent of silver and the absolute value of the faraday it is neces- 

 sary to learn the amount of "inclusions" in the silver voltameter de- 

 posits. Lord Rayleigh 1 advocated heating the platinum cups with de- 

 posits to incipient redness as the simplest method of expelling the in- 

 clusions, which are chiefly water and silver nitrate. Richards and An- 

 deregg 2 have recently used this method also, finding the inclusions to 

 be large and variable in amount. 



When silver deposits are heated in the platinum cups alloying of the 

 two metals takes place, and on removing the silver the platinum cup 

 shows stains which are brownish or black. 



We have found that these stains are platinum black and that they 

 render the weight of the empty platinum crucible very uncertain unless 

 the precaution is taken to heat the cups to incandesence, or to remove 



1 Phil. Trans. A. 175: 411. 1884. 



2 J. Am. Chem. Soc. 36: 15. 1915. 



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