Chemistry and Physics. 75 



inexpensively, as glass. It may be thickened by adding fresh 

 rings of silica, and all kinds of joints can be easily made. In one 

 respect silica is easier to work than glass. It never breaks when 

 suddenly thrust into the flame, and the finished apparatus needs 

 no annealing. For this work the eyes must be protected by very 

 dark glasses. 



Vitrified quartz is harder than feldspar, but less hard than 

 chalcedony. When cut with a file it breaks like glass. Its con- 

 ducting power for heat is about equal to that of glass. Its den- 

 sity, 2-21, is much lower than that of quartz, 2 '66. It has been 

 found that the coefficient of expansion by heat is only Jl_ as 

 great as that of platinum, and much smaller than that of any 

 similar substance that has hitherto been studied. The substance 

 is shown to be remarkably transparent to ultra-violet rays, hence 

 its application to spectroscopic work will probably be important. 

 Perhaps the most remarkable property of vitrified silica is its 

 resistance to sudden changes of temperature. Water may be 

 dropped upon a white hot rod of the substance, or a similarly 

 heated tube of it may be plunged into cold water or even into 

 liquid air without injury. It is suggested that the material will 

 be useful in the preparation of thermometers, for instance, those 

 in which tin is used in the place of mercury, and also for the bulbs 

 of air-thermometers. The interesting observation has already 

 been made that when oxygen and nitrogen (air) are heated above 

 the melting-point of platinum in a silica tube, nitrogen peroxide is 

 produced. — Chem. JVeios, lxxxiii, 205. h. l. w. 



4. Influence of Magnetism upon Supersaturated Solutions. — 

 Attempts by A. de Hemptinne to produce the crystallization of 

 supersaturated solutions and supercooled fusions by exposure to 

 a strong magnetic field were in every case failures. By indirect 

 means it was shown that crystalline substances in saturated solu- 

 tion showed a distinct orientation in this field ; hence it is con- 

 cluded that crystallization in these cases does not depend upon 

 the orientation of the molecules. — ZeitscJir. physihal. Chem., 

 xxxvii, 223. h. l. w. 



5. The Preparation and Properties of Ammonium Cyanate. — 

 This salt was not obtained as a solid in a pure condition by Liebig 

 and Wohler, on account of its transformation into urea. Walker 

 and Wood have recently succeeded in preparing this famous salt 

 by mixing solutions of cyanic acid and ether at —17°, and also 

 by mixing the gases diluted by air. It is a colorless salt which 

 is readily soluble in water, and this solution gives the reactions 

 for the cyanate and ammonium ions. Upon heating it fuses at 

 80°, but then becomes solid again, being changed to urea. — 

 'Jour. Chem. Soc, lxxvii, 21. h. l. w. 



6. Detection of Selenium in Sulphuric Acid.— It has been 

 found by Jouve that crude acetylene gas furnishes a very delicate 

 test for selenium in sulphuric acid by precipitating it in the ele- 

 mentary condition. He states that a red coloration can be observed 

 when the acid contains only one part of selenium in 100,000, while 



