Bose, C R

Sen, Ranjitkumar

English

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ON THE AXIAL LENGTHS OF PHLOROGLUCIN DIHYDRATE CRYSTALSBy  C. R. BOSEANDR A N jr i'K U M A R  SEN{Kcicivcd for publication, April 28,ABSTRACT. The iixiul lengths of Plilorogliicin Dihydrnte crystals have l)eeii accurately rtctcrniined. The va 111 e.s obtained arc (1 = 6.740 A.u., h-S.ogo A.ii,, r= 13.6.14 A.u, The axial ration determined from goniometric inensurenients (jf the cry,slnl are a: h : c .83^ 4 : j : 3.366. The density of the crystal is found to be 1.453 gms. per c.e(Jii examining the axial ratios of Phlorogluoin Dihydrale crystal given in Oroth’s Cliemische Kristallographic (Vol. IV , p. <S())and the ratios of axial lengths found from X -ray study (Hanerjee and Ahmed, 1038) a discrepancy appeared which was much higher than the limits of accuracy usually attained in such experiments. So it was thought useful to repeat these measurements.The axial lengths were measured from rotation and o.scillation ]>hotographs ill a cylindrical camera of diameter 8 .3  cms. Hoth copper and iron K „ radiations from a Madding tube were used for this purpose.A  small crystal was mounted successively with the three crystallographic axes parallel to the rotation axes by the hel|> of a t'/.apski two circle theodolite goniom eter.^,111 order to eliminate uuccrtamlics in the determination of the diameter of the camera due to want of axial symmetry of the camera if any, fine aluininiimi powder was dusted on the crystal. The diameter of the camera was thus determined accurately from the aluminium lines for each photograph sepa­rately. This also removes any error arising in the process of mounting the film in the camera.To obtain the layer line distances, the distance between pairs of correspond­ing spots on two layers of the same order one above and one below the equatorial line was measured. Half of the mean of these distances was taken as the layer line distance for that order. The axial lengths were thus calculated separately from different layer lines for the three axes. The mean values of the axial lengths thus obtained were« = 6 .7 4 4  A .U  , 6 = 8 .0 9 3  A .U ., c = i 3 . 6 i 5  A .U .These values of the axial lengths were used for indexing the diffraction spots whose positions were accurately determined. Very accurate values of the axial lengths.*3„ i 455P _ m21164 C . R . Bo$e and R . Senwere thus obtained. Very small crystals were used so that the diffraction spots wei'f appreciably small. With the help of the calibrated diameter of the camera the angles of reflection of tliese s.])ots A\ere calculated. The results of the measure­ments are given in 'I'able I where the first columu givc.s the indices of the planes,the second gives 2O, the third and the fourtli give d a n d o r  ^  + +respectively, whence a, b and c have been calculated.Table 1Planes 2dAxial lengthsj a b6‘ »o 86'’36'; 1 2.122 j 793 6 - 7 3 3  . —006 2.26.1 .195 — — 13.5^9u8o T .012 .077 8.096 --008 69“i s ' 1.702 ^345 — 13.616,00(10) 9 o \3 7 ' 1.361 -54“ — — i3,6xt>630 9 5 ’45' 1.039 .9636.745 S.085650 .t)22 1.083 1nep I2 4 "4 8 ' 868 ' ^'3251 6.7361! 8.0907o"4 4 ' I 3^0 ; .566 1 14m 5 4 °4 5 ' ' 1 .t-;'!1-33716.7,16 ! x.3-5954 t u 1 ; I 687 35 J j4t)2 j .St)-;' 1.637 ; -373 ... 13.615Mean value of the axial lengths :—rt-6.740 A,T.T,, b -  8.090 A .r , c =  13.604 A .r.The crystals were also studied by a two circle theodolite goniojnetei*. A  few- good crystals wdth well-developed faces were chosen and each was mounted successively wuth the three crystallographic axes vertical and the interfacial angle betw^een the corresponding zone faces were measured by the horizontal circle. The mean value>s from the measurement of several crystals are given belowm : 111 (n o ) : (n o) =  79"'32^r ; r (101) : ( t o i ) =  27^47'The interfacial angles as quoted by Cxioth :—ni : ni (n o ) : (n o) =  79'"!' r : r (101) : (toi) =  27''8'Axial Lengths of Phloroglucin Dihydrate Crystals 165T h e axial ratio a ; b obtained from our measurement of the iuterfacial angle (n o) ; (n o ) came out to be .8324 : 1. The axial ratio b : c obtained from the interfacia] angle (loit) came out to be I : 3,366Thus from the interfacial angles we have :—  a : b : c : : .8324 : 1  ; 3.366The axial ratios from the X-ray nieasureiiieuts are a : b  ■. c ,8333 : x : 3,362The ratios from the Groths’ quoted values arc a : b : I 8261 : 1 : 3 | i 72'Die density of the cryslai \\ as (letennined by ketgei s susitension niethed troni a solution of zinc suliiliate in water. Very .small p artii'esfj0111 flawles.s crystals were used. Several observations were taken and the mean value of the density was found to be r.453 gins, per c.c. The numbtr of 11 olccu'es per unit cell thus came out to be .fj. 'I'lic density of the crystal wa;~ also calculated fioni the mean value of the axial lengths detennined by us and was found to be 1.442 guis. per c.c.Our grateful thanks are due to Jhof. ,S, N. Bose for his kind interest in the work and to Dr. K . Banei jec for suggesting the problem and guidance.Dacca t'NivKRSilv.R B F E R  R N C EBanerjee and Ahmed, 193R, h id .  fourn. P hys.,  12, 249'

On the Axial Lengths of Phloroglucin Dihydrate Crystals

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On the Axial Lengths of Phloroglucin Dihydrate Crystals

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