Chemistry and Physics. 73 



resistance thermometers reading to 00001° practical and con- 

 venient. For further details reference must be made to the 

 original article. — Jour. Amer. Chem. Soc, 39, 2110. h. l. w. 



5. The Detection of Carbon in Inorganic and Organic Sub- 

 stances. — Ernst Mueller has described a general method for the 

 qualitative detection of carbon. A mixture of about 002 g of 

 the substance to be tested is mixed with roughly 20 times its 

 weight of potassium trinitride, KN 3 , and the mixture is heated 

 gently at first, then finally for two minutes at a red heat. Potas- 

 sium cyanide is formed when carbon is present in any form and 

 this may be detected in the usual way by conversion into Prus- 

 sian blue. The test, which is rendered still more delicate by the 

 addition of a little metallic potassium to the reaction mixture, 

 can be applied not only to organic compounds but also to steel 

 and carborundum. — Jour, prakt. Chem., 95, 53 (through C. A.). 



h. l. w. 



6. The Extreme Ultra-Violet Spectra of Helium, Hydrogen, 

 and Mercury. — The region of the spectrum between the shortest 

 wave-length (about 590 A) obtained by Lyman and the longest 

 X-ray wave-length (approx. 12-3 A) given in Siegbahn's tables 

 is a very important one, hence the recent investigation of one 

 end of this gap by O. W. Richardson and C. B. Bazzoni merits 

 special attention. The most serious difficulties encountered by 

 Lyman in his important work with the so-called vacuum spec- 

 trograph were (i) the absorption of the radiation in question by 

 the two meter layer of gas between the luminous source and the 

 photographic plate, (ii) the fogging of the plate by the fluores- 

 cence excited in the gas, and (iii) the introduction of traces of 

 impurities in the gas. It is practically impossible to prevent 

 contamination when the apparatus cannot be heated and when 

 the discharge takes place in the gas itself. To avoid the limita- 

 tions apparently inherent in the vacuum spectrograph, Richard- 

 son and Bazzoni designed and used a complicated quartz appa- 

 ratus which could be kept at a red heat until all occluded gases 

 had been pumped out prior to the introduction of the pure gas. 



The most essential features of the quartz apparatus and the 

 functions of its various parts may be briefly described or 

 explained as follows. One cylindrical portion of the system 

 contained a tungsten filament, a copper plate anode, and an 

 auxiliary copper wire anode. The tungsten filament was used 

 as a thermionic source of electrons for exciting the radiation in 

 the gas. The cylinder just mentioned was connected to a larger 

 quartz chamber by a tube of rectangular cross-section made of 

 the same material. This tube contained a pair of condenser 

 plates which prevented the passage of electrons and ions from 

 the cylinder to the vessel beyond. The ultra-violet waves could, 

 of course, pass unhindered between the plates. After entering 

 the chamber the waves fell upon a copper target and liberated 

 photo-electric electrons. At 90° and at 180° from the target 



