abstracts: CERAsncs 49 



Exceptionally large volumes of "pure" fractions are obtained which 

 have a ver\' small boiling-point range, showing that they contain only 

 negUgible amovmts of impurities. Almost all of each of the components 

 of the mixtiu-e distilled is obtained in practically the ptu-e state, since 

 the volumes of each of the intermediate fractions are only about 1.5 

 per cent of the volume taken for distillation. The composition of each 

 of the intermediate fractions is actually determined, and the error in- 

 troduced by this determination is small, since it is apphed to only small 

 voliunes. The apparatus works well on mixtm-es containing widely 

 var\"ing percentages of benzene, toluene, and solvent naphtha. 



F. M. W. 



CERAMICS. — Use of optical pyrometers for control of optical glass 

 furnaces. Clarence X. Fexner. Bull. Amer. Inst. Min. Met. 

 Eng. looi-ioii. July, 1919. (Geophysical Lab. Papers on 

 Optical Glass, Xo. 13.) 

 Among the features of careful control required in the manufactm-e 

 of optical glass, that of the regulation of fmnace temperatures is of 

 high importance. It was fotmd that the thermocouples generally in 

 use did not come up to the requirements for rapid determination of 

 temperatvu-es, and it was thought that optical pA-rometers should be 

 a satisfactory- substitute. Before adopting them for general use, tests 

 were made to determine to what degree the requirements were satis- 

 fied. As a result, it was fovmd that the manufacturer's calibration 

 tables were considerably in error in some cases (which impHes that they 

 should always be checked \ and that the lu^linosit^• of fmnace-walls 

 agrees satisfactorily with that of a "black body" under some condi- 

 tions but departs ver\' widely luider others. The reason for these 

 results and the factors upon which they depend are discussed. The 

 manner in which the p\Tometer is used under working conditions is 

 described. The conclusion is reached that when the readings of the 

 p^Tometer are properly checked by such tests as these the instrument 

 gives a ver^* satisfactory- and reliable means of controlling furnace tem- 

 peratures. C. X. F. 



