The infrared sp ectra of coesite, low-temperature tridymite, low-temperature cristobalitelow-~emperature quartz, vitreous silica, hexagonal Oe02, tetragonal Ge02, and vitreous germallla are reported from ~,OO O to 300 C~-l. Wherever possible an assignment of frequencies has been made on t he basls of the selectlOn rules for the crystal symmetry. Three characteris.tic gro up frequencies. near 1,lOq, 800, and 480 cm-1 are common to all the polymorphs of Sl02. Thes.e frequ~nCle.s respectlvely correspond to a str~tching mode i nvolving displacements assoclated prnnanly wlth the oxygen atoms, a stretclung mode involving displacements associated primarily . wi~h the. sil~co~ atoms, and a Si-O bending mode. The presence of these gro up frequencles III coeslte mdlcates that t he coordination of silicon in coesite is tetrahedral and that its high density is associated with the packinrr of tetrahedral units at an angle approximatiI?g 120 degrees.. The tetragonal and hexagon~l GC02 polymorphs show a marked dlfference III spectra due III part to the change from sixfold to fourfold coordination. The assignment of obscrved frequencies in hexagonal Ge02 is consistent with that made for low-temperature quartz if allowance is made for the heavier mass of t he Ge atom.

A p ress ure ce ll ,--as constructed usin g a pair of type II d ia monds for sL ud y of infrare d spectra of solids in t he 1-to l5-micro n reg ion . Usin g co mme rcia l infra red equipme nt, spectra can be st ud ied routin ely to calculated press ures as high a s 30 ,000 atm osphe res. U nde r pressure, bands ge nerall y shif t to higher fr eque ncies a nd decrease in in ten s ity. The m agni t ude of bo th cha nges dep ends on the mode of vib ra t ion. Occasion a ll y m ajor cha nges in s pectra occur. In calcite the carbon -oxyge n symme t ri c st retchin g, m od e v" becomes a cti ve a t ele vated press ures while the do ubly dege nera te V3, sLretching, < Ind "4, bend ing, f,' (,-quencies spl it . F l'Om t he s hi ft in frequency of v, wiLh pr e~s ure the " compressibil it..v", [( -l / R o)(dR/dp)]' of the C-O bo nd le ngth, R, is calcula ted to bp 2.8 X IO-7/ atm os phere. :'Iia:i or spec tral ch a nges are no t observed in the sa me press ure ranges in other car bonates hav ing the calcite or aragonit e s t r uctu res. Thc rCR ult s for calcit e may be expla in ed by a shif t of the COs ion fr om the trigo na l axi s und e ,' press ure.

The system PbO-B20 3, of interest to investigators and manufacturers of ceramic glazes and glasses, was studied by well-known methods involving quenching and petrographic examination. In addition, limits of liquid immiscibility were obtained by direct observation. Seven crystalline forms of binary compounds were found and the chemical compositions of six of these established. A number of compositions were studied also as glasses to obtain data on thermal expansion, softening behavior, and relative solubility.

Theory of the method.-The pore volume is measured by allowing the gas which fills the pores to expand into a measured volume and measuring the accompanying fall in pressure.Applicability.-The method is in general applicable to pieces of any size and shape and to all classes of porous bodies or materials.A new porosimeter.-For rapid work with shaped test pieces a new porosimeter is described. The new instrument measures accurately both pore volume and bulk volume. A complete porosity determination can be made in 5 minutes.The results on ceramic bodies arc reproducible to one unit in the first decimal place of the per cent porosity. Considerably higher accuracy than this can be secured if desired.Results.-The results obtained with the new method are in all cases higher, in a number of cases very much higher, than those obtained by the methods of liquid absorption in current use. For fired bodies the same results are obtained with dry air, hydrogen or helium as the pore filling gas. The results show conclusively that complete filling of all the pores in a reasonable time can not be secured by any of the current methods using a liquid as the pore filling agent.No weighing is required.

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