A study has been made of the transmittance of near infrared energy by a number of binary glasses. Of the systems studied, the lithia-silica and lead oxide-silica were found to have the highest transmittance of cnergy ill the range of wavelengths from 3.0 to 5.0 micron s. Thc' t rallsmittance of lithia-silica is compared with that of 1.he other alkali-silica glasses. Values of transmittance are given for lead silicate glasses of highcr lead eontellt than have been previously reported in the literature.

All curves demonstrate the reproducibility which can be attained with the apparatus.A study has been made of the transmittance of near-infrared energy by a number of binary glasses. Of the systems studied, the lithid-ailica and lead oxide-silica glasses were found to have the highest transmittance of energy in the range of wave lengths from 3.0 to 5.0 microns. The transmittance of lithid-silica glass is compared with that of the other alkali-silica glasses. Values cf transmittance are given for lead silicate glasses of higher lead content than previously reported in the literature.

(3] Thermal proper t ies of petrole um produ cts, NBS Misc. Pub . J\I97 (1929 An a nalysis has been made of t he absorpt ion ,bands of v ario us g~asses. by calcula ti?n of t he inte rnal t ransm ittances and surface losses. The waveleni1; t hs,. Ill ~ICrons , assocIated wi th broad a bsorp tio n bands ha ve been m easured , a nd t he a ctIve vIbratll;g grou ps cau smg t he a bsorp tion are a s follows : 2.7, CO2 ; 2.75, OH ; 2.75, CO2; 2. 9, OH asso Cl at~d ; 3.5, C O~--; 3.65, (N 0 3-) ; 3.8, Si -O bond ; 4. 0, C0 3--; 4.15, (N 0 3-) ; 4.25, CO2; 4.45, SI-O b?ncl ; a nd 4.7, OH associated . The g rea tes t lo s~ of infra red e neygy fo r a num be r of glasses IS cau sed by surface losses, rathe r tha n by tr ue m te rnal a b orptlOn.

An apparatus and method for removing by vacuum fusion the gases dissolved in glass a nd for determining the quantity of gases are deseribed. Determinations of gases in three types of optical glass and seven commercial glasses were made. Approximately the same quantities of water were found in the optical and the commercial glasses, but the total volume of other gases, snch as CO2, SOz, Oz, etc., never ex eedcd 10 ml per 100 g of optical glass, while the window glass contained from 34 to 73 ml per 100 g of glass. In the optical glasses, especially the light barium crown glass, there was no indication of a rel ation between the quantity of gas obtained and the number of "seeds" in the glass, nor was there any significan change in th e gas content of the glass during the stirring and fining periods.

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