ABSTRACTS OF TECHNICAL ARTICLES 321 



ber of possible means by which energy may be dissipated in a dielectric; 

 there may be losses due to free ions and also due to dielectric polariza- 

 tions other than dipole polarizations. However, in many materials 

 dipoles are an important source of loss; it is the purpose of this paper 

 to consider some of the typical cases of dipole loss and to point out some 

 of the relations between chemical composition and dipole loss which 

 follow from the recent experimental and theoretical study of dielectric 

 behavior. 



Order-Disorder Transformations in Alloys.'' Foster C. Nix and 

 William Shockley. An extensive resume of a subject which is 

 becoming of increasing interest to physicists and metallurgists. The 

 article divides into two parts, forty pages being devoted to the theories 

 of the order-disorder phenomenon, and twenty pages to experimental 

 studies of superstructures. 



Thyratrons for Grid- Controlled Rectifier Service.^ G. H. Rockwood. 

 It is common knowledge that the output voltage of a rectifier fluctuates 

 with changes in load current and supply line voltage. Frequently 

 these fluctuations are so large that means must be used to correct them. 

 This is particularly true when the rectifier feeds a load having a high 

 back electromotive force and a small resistance, such as a storage bat- 

 tery. The facility with which the output voltage may be controlled 

 by the use of thyratrons as the rectifying element has encouraged the 

 design of tubes especially suited to this purpose. There is available a 

 variety of circuits such that the output voltage of a rectifier may be 

 made to obey any desired law. The successful application of these 

 circuits depends upon the degree of reliability of the thyratron tubes 

 used in them. To be most successful the tubes must possess certain 

 characteristics. This paper gives a brief review of the operation of 

 grid-controlled rectifier circuits, discusses the requirements which such 

 circuits impose on the tube characteristics, and describes a particular 

 type of thyratron with mercury-plus-argon filling which has proved 

 especially useful in such rectifiers. 



Progress in Non-ferrous Metals and Alloys During the Past Few 

 Years.^ Earle E. Schumacher and Alexander G. Souden. The 

 purpose of this review is to present the more important advances in 

 the non-ferrous field during the past few years, the topics discussed 

 being classified broadly as fundamental and practical. The former 



^ Reviews of Modern Physics, January 1938. 



* Trans, the Electrochemical Society, Vol. LXXII, 1937, pp. 213-224. 



^ Mining and Metallurgy — Institute of Metals Division, January 1938. 



