Samples of ar~e n i c s ulfid e glaHS " -ere investigated to clc>lerll1ine the ir che m ical a nd phys ical properties. Amon g the proper ties r eported a re t ile hygros co pici t.I', chemi cal durability, hydroge n e lec trod e fUllc t ioll, ex pansivi ty , clastic nlOduli, modulus of rnpture', hardn ess, transmittance, and indices of re fraction .The main in te rest in "rse n ic s ulfid e glass, for t he prese n t, is for i ts lrnnslIliitance in t he i nfrared. It is transparent, t o infrared energy out to "PPr'Oximately l3 microns. Although its pl\I'8 ic:<1 prope rt ies a re inferior to those of ordi na r.l-s ilicale g ln"e,.; . th('~' nrc s up e rior to t hose of some of the ,wail ab le maleria,b used in infrared o pl ic'_

The infrared transmittance of some calcium aluminate and germanate glasses has b ecn measured out to 6 microns. The range of compositions of the calcium alum inate glasses was CaO , 26.7 to 52 .0 pOl'cent, and A1z03, 28.2 to 49.6 perccnt. Barium oxide, BeO, Bi20 3 • La20 z, MgO, a nd PbO were added in varying amounts up to a maximum of 36.0 percent for anyone constitucnt. These calcium alumi nate glasses are good infrared t ransm itters but show a prominent water absorption band at 2.9 to 3.0 m icrons. This absorption ca~ be decreased somewh at by means of a dry air t reatment of the melt. Thcse glasses have a st rong tendency toward devitrification .Ge rmanium oxide is a good glass-fo rmer. Its glasses have about the same infrared t ransmi ttance as the calcium aluminate glasses in the absence of ox ides such as Si02 and BcO, " ' hich absorb in the '1.5-to 5.5-micron region .

The pH ~·espo.n.s e, hygroscopicity, and chemical durability of a series of Na,O-PbO-Si02 (soda-lead oXlde-slhca) glasses have been investigated . The results obtained ar~ in complete acco:d WLth the data prevIOusly publls~e.d fOl: a series of N a20 -CaO-Ri02 glasses and show t~at. 1. Glasses of very: low hy~r~scoplclty YIeld electrodes whose pH responses fall appreCiably below ~he theoret.lcal 59 I11Ilhyolts per pH at 2.5 0 C; 2. electrodes prepared from glasses of P?or chemIcal dU:'ablhty also fal~ to d evelop the full theoretical voltage. . Vi ~en the app~ox lm ate compOSItIOns at wluch changes in the primary phase appear for the Na20 -PbO-SI02 system .are supenmposed upon the pH response and chemical durability c.urves, the marked ch[Lnge.s 111 t l? ese properties appear to reflect some of the criti cal compositions of the phase eqUIlibrium d iagram .. The chemical dura.bilit~ data obtaiI? ed b y the interferometer procedure indicate that the pioperty ?f swellmg 111 aCid solu tions IS much more universal for sili cate glasses than previously realized.