248 BELL SYSTEM TECHNICAL JOURNAL 



appear to be present in a dispersed state in the hydrocarbon. The 

 particles are shown to contain about 18% of water, determined as 

 water of retention in pressed coagulum. 



The "resins" have been separated from both types of balata latex 

 as water-white viscous liquids which deposit crystals of j3-amyrin 

 acetate on standing. The red balata latex resin is shown to be more 

 viscous than the white and to differ from it as regards its iodine value, 

 refractive index, and solubility in cold 95% ethyl alcohol. 



The serum constituents have been separated into four main frac- 

 tions: protein, carbohydrate, gummy substance, and ash. Minor 

 constituents such as tannin and amino-acid have also been noted. 



A complete analysis of balata ash has been made and compared 

 with the analysis of ash from Hevea latex by Bruce. Balata ash was 

 found to contain higher contents of CaO, Na20, and MgO and lower 

 contents of K2O and P2O5 than Hevea latex ash. 



New data are presented on the density, refractive index, dielectric 

 constant, and heat of combustion of balata hydrocarbon which are 

 believed to be more reliable than similar data previously available in 

 the literature. Data on the effect of temperature on the refractive 

 index of balata and gutta percha hydrocarbon are presented, showing 

 the crystallization of the gutta hydrocarbon on cooling, which starts 

 at about 37° C. resulting in an abrupt increase in refractive index 

 occurring between 37° and 35° C. 



A Short-Wave Single- Sideband Radio Telephone System.^ A. A. 

 Oswald. There is described briefly a short-wave single-sideband 

 system which has been developed for transoceanic radio telephone 

 service. The system involves the transmission of a reduced carrier or 

 pilot frequency and is designed to include the testing of twin-channel 

 operation wherein a second channel is obtained by utilizing the other 

 sideband. 



The paper indicates the reasons which led to the selection of this 

 particular system and discusses at some length those matters which 

 require agreement between the transmitting and receiving stations 

 when single-sideband transmission is employed. 



The Oxide-coated Filament. The Relation between Thermionic Emis- 

 sion and the Content of Free Alkaline- earth Metal.'' C. H. Prescott, 

 Jr. and James Morrison. The oxide-coated filament had its begin- 

 ning in the sealing-wax era of vacuum technique. The obscure acci- 

 dent of its origin is not recorded, but all of our older physicists knew 



6 Proc. I. R. E., December 1938. 



' Jour. Amer. Chem. Soc, December 1938. 



