530 Mr. W. A. Shenstone [March 8, 



silica expands quite regularly, and much more rapidly than vitreous 

 silica up to 570°, but that at this temperature a sudden and considerable 

 expansion takes place which is followed by a steady contraction 

 on further heating. 



One of the most important fields in which vitrified silica is likely 

 to be useful is that of thermometry. 



Owing to its small co-efficient of expansion, the degrees of silica- 

 mercury thermometers will be of greater length in proportion to the 

 volumes of their bulbs than those of glass instruments. Owing to 

 its high melting-point it should be possible to employ it with 

 advantage for the measuring of high temperatures by replacing the 

 mercury by tin or other metals, as has been done by M. Dufour.* 

 And whilst the great elasticity of vitrified silica suggests that the 

 fixed points of silica-mercury thermometers will be much more stable 

 than those of glass-mercury instruments, the impunity with which 

 it may be suddenly cooled from high temperatures promises obvious 

 advantages. 



Again, the high melting-point of silica should make it very 

 valuable for use in platinum thermometers, and I exhibit such a 

 thermometer to-night which has been fitted up for Professor 

 K. T. Glazebrook. But as the applications of vitreous silica in 

 thermometry are still under investigation, I will not dwell on this 

 part of the subject, excej)t to add that as glass reservoirs for air 

 thermometers have proved disappointing, I am not without hopes 

 that the new material may prove helpful in that department also. 



We have not yet had time to examine the behaviour of silica with 

 solvents, but, if it acts like other forms of the same compound, it 

 may be expected to replace platinum for some purposes, as, for 

 example, for condensers for the preparation of pure water, and vessels 

 of silica probably would be much more suitable for use in exact ex- 

 periments on the freezing-points and boiling-points of dilute aqueous 

 solutions, than the glass tubes now often used for such work ; but, of 

 course, silica vessels will be very susceptible to the action of alkalis. 

 Finally, silica may be expected to prove more suitable than glass for 

 use in researches on pure gases owing to the qualities of its surface, 

 and for use in experiments concerning the behaviour of gases at high 

 temperatures. We have already one small application of silica to 

 research in this latter field to put upon record. 



It is well known that nitrogen and oxygen enter into combination 

 under the influence of electric discharge, and Sir William Crookes f 

 has shown that oxides of nitrogen are present in considerable 

 quantities in the flames which accompany the discharges of large 

 induction coils ; but although various observers have reported indica- 

 tions of the presence of nitrous fumes in the neighbourhood of flames, 

 the forming of an oxide of nitrogen from nitrogen and oxygen alone, 

 and without the intervention of electricity, has not, so far as I am 



* Comptes Rendus, cxxx. 775. f Chem. News, lxv. 301. 



