Krishnamurti, V G

Rao, K R

Sastry, M G

English

IACS Institutional Repository

42 ULTRA·ViOlET BAND SY~TEMS OF THE MERCURY IODIDE MOlECUlEr-PART I By K. R. RAO,* M. C. SASTRY AND:'V. C. KRISHNAMURTI (Plate VII) ABSTRACT. The ultra·yiolet bands of the mercury iodide, excited in a discharge tube, are photographed with a Hilger large quartz Littro", spet'trograph. Thl: systems C and D lying in the regions ~3100 -. ~2800 and A28uo - A2650 art llJea~urcd. The wavelengths of the C system are compared with those published by Wietalld, thl' data obtained in th~ system D being entirel~' new. Analysis of the two systems have led to the following vibrational constants-v, '" xol '" " x"w" System C : 3~73O·9 235. 6 2.16 125·9 1.07 System D : 36269. 2 178 .0 1.14 125.7 1.10 . They arc in agreement with the values determined approximately by Wieland from the study of fluorescence of HgI. The origin of the D system is, hClI\'ever, diffcrent from that suggested b.v Wieland. With the c1a5sification obtained in the present work, the s~·gtellJs could b~ attributed to the two components of a n2".-2Ji eketronit' transition with a gn interval of 3538 cm- I which is sh~)wn to be ill conforlllity with the corresponding i1lt.ervals obtained for the other mercury halides, HgF aud HgCI. INTRODUCTORY The mercury iodide molecule has:an extensive band spectrum in the ultra-violet. Wieland (I929) investigated these bands with a grating having a dis-persion of loA. per mm. in the first order and quartz. spectrographs of nearly the same dispersion at A2500. The systems reported by him are shown in Table I, together with those observed by later investigators, Prilheshejewa (1932) and Sastry (I942) TABLE 1 Author Region Previous Present designation designation ------ ..• --.--.'~.'. -'-"-~. Wieland ... ... .... 4500-3400 Class III B ..... 3100-2800 " II C ...... 2800-2650 ? " I D ...... 2700? 2530 ...... E Sastry ... ... ... 2560.-- 2530 Class A 11 Prilheshej ewa ... ... 2240-2168 ...... G ...... 2160-2114 ...... R - In his earlier work Wieland loc. cit. investigated these bands in emission but the wavelength data were given only for the system C. Although no analysis ·Fellow of the Indian Physical Soc;iety. 324 K. R. Rao, M. C. Sastry and V. C. Krishnamurti was presented, certain regularities were indicated among the bands of this system and the bands themselves were ascribed to the triatomic molecule Hg lla' In later work, studying the absorption and fluorescence of the vapour of mercury iodide, Wieland (1932) ascribed these bands to the diatomic molecule. By optical excitation of the vapour by sparks from different metals and using suitable filters, fluorescence spectra were obtained which were associated with the equations HgIg + Izva~HgI A: + I Hglk~HgI + hVf where the difference Oll'. -//1'/) :> the dissociation energy of HgI2~HgI+1. The fluorescent systems were measured and from a study of their structure, the following approximate formula:: were suggested, System c: v= 32784 + [233.3V'- 2.25v/2] - [I24.oVll - J.()Vll2] System D: v=36J30+ [175v'-I20V"] For system B no anaiysis was given but the occurrence of the wave number intervals 120 and 180 was mentioned, which is suggestive of the probable elec~ tronic transition illvo)ved ill their emission. One of the writers (Sastry, 19.P) published the wavelength data of the system E obtained in emission with a Hilger El quartz Littrow spectrograph and in addition obtained a new system between A'\2530 - 2560 (desigllated by him as class A but hereafter will be referred to as system F in conformity with the designation of the other systems). The system E was found by him to consist of two components 0(1 and {31 having a common final state and an electronic width of about 766 em-I, The system F was attributed by him to a transition !In - 2l; showing four component heads and an electronic separation of I26 wave number units. As was mentioned by Sastry, the analysis does not show any level in comDlon with the other bands of HgI. In view of this, a reinvestigation seemed desirable to systematise the analysis and interpretation of all the known bands of mercury iodide and to examine if they can be corre-lated with the band systems of the other mercury halides. As a first step, the systems 'C and D are considered in this paper, a preli-minary report of whicb appeared in Current Science (in press). Both the systems are newly photographed and measured, as no wavelength data appear to have been published at all fQr system D and system C was obtained by Wieland with a comparatively lower dispersion instrument. EXPERIMENTAL The bands were excited in a pyrex discharge tube about 10 ems by 1.5 ems diameter, containing mercury iodide in a small side bulb which could be heated if necessary. The excitation was either by a quarter-kilo watt trans-former giving about I5000 volt or by a small 8 inch induction coil. Continuous evacuation by a Cenco-Hyvac pump was necessary. The discharge was bright violet and could be maintained. easily for hours with just occasional heatinir Ultra-violet Band Systems of the Mercury Iodide Molecule 325 of the mercury iodide container. Two Hilger quartz spectrographs were used for photographing the spectrum, the measurements being made by the larger one of the Littrow type with a dispersion of 3.8A per mm. at '\2800. The measurements, made by a Hilger measuring micrometer, are the average of three independent settings. Iron arc lines were used as standards for deter-mining the waveleng.ths. The spectrum is shown in plate VII. In both systems the bands on the Ions wavelength side have somewhat sharper edges, getting diffuse as they occur towards shorter wave lengths. At the extreme ultra-violet end, they are very crowded, exhibit no edges at all and are diffuse and mostly unresolved. In me.uring the plates the micrometer settings were made against the edges of the bands where they are sharp and against the central maximum where they at;C diffuse. About 130 bands are nieasured in system D. Table 2 gives the: wavelengths and wave llumb(;rs of the heads, the intensities being the usual visual estimates. ANALYSIS The fourth column in the Table 2 gives the assignment of the vibrational quantum numbers, as determined in the present work. About 90 bands are classified. A few of the bands arc assigned twice. (lne difficulty met with, in working out the analysis, is the ambiguity in the possible assignment of the bands lying particularly in the extremely cro""ded region below about '\2700. This makes the classifications in this part of the spectrum somewhat uncertain. There is need for photographing this region with a much higher dispersion in order to clear the ambiguities. The following formula is calculated to represent the band heads : ·v= 36269.2 + [178.0(11' +~) - 1. 14 (u' + t) 2] - [125.70(1'" + i) - 1. IO(V" + i)2] For about 70 bands the "obs-calc" values are less than 3 units. The larger discre-pancies in the remaining bands are believed to be due to the uncertainties in the measurement and the ambiguities in the classification referred to above. The constants w' and w" agree well with those obtained approximately by Wieland (1932) from the fluorescent system but it will be seen that the system origin is shifted towards the violet by about 160 cms- I . Many of the stronger bands in emission are thereby brought into the scheme of classification. This shift rs also supported by the view advanced by Howell (1943) and discussed in a later paragraph of this paper. The intensities of the bands are shown in the usual diagonal matrix in 1'able 3 which contains also the values of ~G in the upper and lower states. The band spectra of several iodides show an intensity distribution corres-ponding to an open parabola. Such a definite characteristic is not seen in the present bands. The (0. 0) band is no doubt not the most intense and the stronger bands occur in the two progressions v'=o and 1)1/=0. There is however, an asymmetrical development of the sequences, those giving rise to ~ands on the 326 K. R. Rao, M. G. Sastry and V. G. Krishnamurti lower frequency side of the origin being very poorly developed while on the violet side long sequences are obtained for ~'V = + 3 to + 7. TABU: 2 Hg I bands. (System D) Wavelength Int. Wave number Classification (v'. v"') Obs-cal. 2808.88 3 35590·( 0.6 2·3 08 47 3 S¢·2 on 40 2 698.2 0,5 -0.6 00.22 2 70 1.0 27':18.22 2 726,5 2.8 8·4 95.31 2 7637 1,6 0·7 93.0 5 1 792 .7 9129 5 815. 1 0,4 0.6 815.6'; 3 874-7 I,,'; -08 i/3·S l 91].4 S.Il -2·3 82.16 5 932·7 0,3 1.3 80.21 2 957·9 4,9 5.6 77. 1 3 ~ 997.8 3.7 0·4 7497 2 36025.8 73·05 .~ 050·7 0.2 0.2 72.42 3 058.9 4,S -0·7 69.5 1 2 096.9 65.80 2 145.2 64·5° 3 162.2 2,4 -1·5 63·77 3 171.8 0,1 0 59.64 2 226.0 1,2 0.8 57-17 2 258.6 55.60 2 279·0 2.,3 -r.6 4.6 2-4 2754·37 2 36295.3 0,0 0 51 . 16 1 337.8 3,4 2·9 ,';0.46 4 346.8 1,1 -0·7 47·33 3 388.2 4,5 -1.9 45.67 2 410•2 44·29 2 428,5 43.20 442·7 5.6 -0·5 42.66 2 450.2 33 -16 41.17 5 469.9 1,0 -1.1 38.66 3 503·4 4,4 -0·4 37.46 2 519.4 2,1 -1.6 36.49 2 532·4 34-93 2 553. 1 5,5 -26 3369 2 569 8 3,2 -1.1 30.47 3 613.0 28.24 5 (.42.9 2,0 -16 ~642 4 667·3 5,4 -3·1 24·33 2 695·4 21 93 2 727.8 21 12 2 7.,8·7 4,2 -1.1 169° 3 . 795.8 IS·64 S 8129 30 -2.8 1467 4 826.0 110,7 6·9 12.18 3 85.9·8 4,1 -1·3 1I.20 3 873.1 9.8 4.6 10·38 3 884·3 7,5 2.2 09.78 3 8924 c>8.g8 1 903·3 5·2 3·1 08,59 2 908.7 07.58 2 922·4 10.9 4·6 06.96 3 9308 8,6 1·4 05.51 4 950.6 6,3 -1.0 03.27 5 981.2 9,7 4·6 2702.t8 3 36996·2 7.4 -0.6 00.01 3 37025.9 5,r -18 1'0,8 2.2 Ultra-Violet Band Systems 0/ the Mercury Iodide Molecule 327 TABLE 2 (c01ltd.) Wavelength Int. J Wave number Classification ' ,/ ,1/-) Obs~a1. _ ._. ___ . ___ • __ ~,.' __ v._r 2f197.9·1 .2 054·8 8,5 13·8 96.93 2 068.2 6,2 -2,5 96.65 2 072.0 II,9 13 95·80 2 083·8 ... ... 95·51 1 087.8 9,6 0·9 94·34 2 103.8 ... .. , 93-74 2 II2.1 7,3 -1.6 92·72 3 126.2 '" ... 92.24 3 132.8 10,7 1 .. 0 91.27 2 146.2 5,0 -5·0 91.00 3 149·9 ... ... 90.19 2 161.1 8,4 4·5 89.81 2 r66·3 13.1I 1·7 88.87 2 179·3 II,8 2·7 88.07 2 190·4 6,1 -0.6 .87.64 3 196 .. 3 ... ... 87·37 4 200·9 9,5 1·5 86·73 3 208·9 14,12 -2'5 86.07 2 218.1 J2.9 -3·3 85·0 i 3 232.0 7,2 -0.8 84·35 2 242.0 ... ... 83·9.~ 2 247·7 ... ... 8321 2 257·7 15,13 -0·4 82.62 3 2660 13,10 -1.1 81.69 2 278.9 8,3 5·4 81.21 2 285.6 II,7 0·9 80·73 2 292.2 ... ... 7922 2 313.3 14.1I 2.6 9,4 -o.R 78.63 3 321 .4 ... 78.27 3 326.4 12,8 -0·9 2677.29 3 37340.1 ... ... 76.81 3 346.8 ... -I~I } 76·33 2 353·5 10,5 1 15.12 -1·7 75·26 4 368.4 ... ... 74·95 3 3728 ... ... 74·16 I 383.8 ... ... 73·52 3 392.8 8,21 o.:q II.6 2.2 ) 72.72 2 4°3·9 16.13 4·3 71.72 2 418.0 J4,1O 4·8 71·42 3 422.2 ... ... 71.00 3 428.1 ... ... 70·53 2 434.6 9,31 3.6 } 12.7. -0.6 7°·03 1 441.6 17,14 -2,4 59 57 2 448.1 ... ... 6q.24 3 452·7 15,II -1.8 6.Cl·58 2 462 .0 10.4 -7·3 67·80 I 472·9 13.8 -2.8 67·23 2 480.9 7,0 3·5 66·52 2 491.0 16,12 -5·7 65.81 2 500.9 II,S -6.6 64·82 3 514.8 14.9 } -1.1 J 8,1 1.4 63·64 4 531·5 ... ... 63.19 0 537.8 12.6 -74 62·48 ' 4 547·8 9,2 " -2·3 61·30 5 564·4 15,10 -26 60,76 4 S72.1 ... I . .. 60.07 3 S8x.8 ... ... 328 K. R. Rao, M. G. Sastry and V. G. Krishnamurti TABLE 2 (eonid.) , Wavelength Int. Wave number I CI~SS~fica~~:".f~<:~_ ____ ~ __ ~_.,_ • .....o..__,_., __ "_ I 59'36 3 ,59 1 .8 16,11 I 58,78 600.1 58 .12 2 609·4 57'·66 2 61 5.9 II ,4 S7.~6 :1 617.3 14.8 .<668 2 629.8 17,12 2654.84 2 .,765.<;.9 12.5 54<,7 (, M2·5 15.<) 54. 00 667 8 53·10 ., 680.,') 52 •83 684.4 13.6 51.46 2 70 3.9 16.10 5"·93 2 7 1 1..1 50.07 " 723.6 14.7 49·59 0 73 0 .4 17, II 48 48 I) 746 .4 11,3 47.4 2 2 761 ,1 15,8 TAB/,l~ 3 Intensity distribution in Hg I lunos (System 0) ,) I 2 3 4 s 6 7 8 9 10 11 12 13 14 IS 16 17 ----_. 6G" ('lI+l) 2 5 ."> 5 5 2 I 2 i --'" I 2/ I 3 5 4 2 2 2 2 3 3 2 3 3 i 2 4 , 2 2 : 3 0 I ~-,' ~ ,.., ... I '3 , c5 '" N ... ... I I 5 I 2 3 3 71 s i 9 i lO I II -3---'-1---:-\---·j----- -2 I I 2 33' 2 I 3 3 2 4 2 1, 3 3 2 2 ~ I 4 : I 2 4 5 I 3 I 2 2 ~I 3 ;\ 2 I , 2 2 2 2. 2 I i 2 "I 2 3 2 I 2 I 3 1 4 3 2 0 3 3 2 2 3 I 2 () 5 3 2 2 I 2 3 2 2 I 0 2 1 I - ---- ------I ,------ ~---. I "--- --_._, _ .. " ~ 'D 'D I '" N ~I ;:i ,.., :71 I N Of ~I "- ~ 8 ... ... :=3 0 0-... ... .::. ... ... I Obs-cal. -4·2 -6·3 -4·5 -6.2 -2·3 28 -97 5·4 ... -6." -4·9 7·3 -4·2 175·(> 172.8 172·3 167.6 164,7 165.5 162.8 165.8 153·5 153·3 151.8 148 .4 147·7 144.0 144·7 140.6 138 .7 ,-_. -> .. --~--. The values of AG shown in this table cannot be considered as very satisfactory, the irregularities are very probably due to the diffuseness of the bands and consequent uncertainties in tht! determination of their wave lengths. Tables 4 -and 5 give the measurements, classification and the intensity distribution among the band:; of system C. About 86 band:; have been obtained, some of them being new. The AG values of the lower state of this system accord Ultra-violet Band Systems 0/ the Mercury iodide Molecuie 329 fairly closely with the corresponding values shown in Table 3 for system D. That these two systems have a common final state is indicated by the following formula calculated for system C v= 32730.9 + [235.6 (v ' +~) - 2.16( v' +~)2] - [125.9(v" +~) ";I.07(v" + 1)2] TABU'; 4 Mercury iodide bands (s,ystem C) Wave-number I I t I Wave-number (Wieland) n lAuthors) 32536.2 ----~----\1--~-5~:3-------··----- 5 Jut 650 .0 4 650·3 3 I 6.<;2·3 ;; 660.0 5 I 66r.] 4 761.3 4 763 1 4 770·9 3 I 772.1 4 782.8 5 784.<) 4 870.1 4 I 872 .8 5 891.6 4 974'7 I 976.6 3 i 988.! 3 <)97.0 2 I 999.6 4 33014.4 3 3301 702 5 3.3 102.4 u8·9 188·7 199·7 506•8 531.0 558.5 589.0 650.6 680.1 711.3 739.2 77I.7 803·1 827,1 858,6 862·0 4 2 3 3 3 2 4 I 4 2 3 2 I 3 3 02] 5 5 33°85·3 I °97.2 1 103.4 3 120.0 3 19°·9 2 0 4.8 222·3 2433 293. 1 319.9 342.2 358 .3 39o .T 416.1 438.6 466.5 479·4 494·5 510.2 520 .6 530 •6 559. 1 589.0 631 .0 649.2 652 .5 739.8 739.8 771 .2 8°3. 1 810·5 831 .5 859·4 2 5 3 5 2 4 4 4 1 1 .) 3 2 5 5 2 4 4 4 3 3 2 2 2 3 Classification 2,2 1,0 4,5 3,3 2,1 5,6 4.4 3·2 2,U 5,5 4,3 3,1 6,6 5,4 4,2 5,3 4,1 8,8 6,4 5,2 Obs-cal. 0·9 4·7 2.1 II 2·3 2·4 o -5·4 2-3 1.1 l.g 2.0 -1.3 0.6 (l.6 7·4 3·0 2.0 o 1 -3·5 0·7 0.2 4·<) -0.1 2.6 } -3.8 \ -3.0 0.8 -0·5 2.6 -3.0 330 k. R. Rao, M. G. Sastry and V. G. Krishnamurti TABl,E; 4 (oontd.) Wave-number Int. Wave-number ; Int. Classification Obs-cal. (Wieland) (Authors) ; ---------------_ ....... "--.. _--33891·9 1 33892.7 3 5,0 } -1.5 ~ 9.7 JAj ... ... 909·6 2 8,5 -7.1 944·2 2 946.1 4 7,3 -02 949·4 2 950 .6 3 ll,10 1.3 9777 I 978.2 3 6,1 -5·9 982 -9 2 ... ... . .. ... 340 28.0 3 340 30 7 4 8,4 -1.2 061.6 I 065·0 2 7,2 -0.8 ... ... 084. 1 2 10.7 2·3 IIO·4 I lIo'7 5 6.0 } 2-8 ~ 9,5 -2·7 ) 143.6 3 144.6 4 8,3 -2·7 186.8 I 181.9 2 7,1 0·4 223. 1 3 .. , ... ... ... 226.0 4 226.2 4 9.4 -2·4 ... '" 263.3 3 8.2 -5·5 3°4.1 3 300.8 4 10,5 -'5. 1 337·2 2 338.9 3 1I,6 } 1.6J 9.3 -7. 1 381.4 2 382 .5 3 8,1 -8.0 408.6 0 ... ... . .. ... 415. 1 1 417.0 3 ... ., . ... ... 423.2 2 10.4 2.1 451.3 0 ... . .. ... ... 457 8 2 460·3 3 . 9.2 } -5.2 } I 12,7 6.6 489·9 2 492·7 2 I II,S -1.3 512.6 1 512 .1 3 ... ." 534.6 0 538,9 3 10,3 -0'4 566 .2 0 5678 3 12,6 3'0 ... ' .. 593·6 2 14,9 0'4 6Il.l () 614·1 4 II.4 4'9 642·9 2 640.8 3 13,7 7'7 676.5 0 677.6 3 12,5 -0·8 715.1 2 716.8 3 ... ... ... ... 726.0 2 16,1I 2·2 34750.7 2 34753.1 2 13.6 9·0 ... ... 764.8 1 15.9 1·2 786'9 0 789.0 3 J2,4 0·4 ... ... 806.6 4 14,7 -2.1 821.5 2 821.0 3 16,10 -5·2 860.3 0 868·3 0 15.8 -2·5 890.8 1 ... ... . .. ... 8<)3·8 2 ... . .. ... .. . 931.6 2 928·9 3 16.9 -1.8 964·6 0 965.0 0 , ... . .. 35000.1 0 35005·0 0 ... . .. ... ... 35040.6 2 16.8 3.2 Isotope Effect.-As iodine has no isotopes, the band spectra of iodides are parti-cularly suitable for the study of the isotopes of the combining .atom-Hg in tbis case. The known isotopes of Hg and their percentage abunc1ance are given below (Seaborg, 1944). 196, Ig8, 199, 200, 201, 202, 204 0.15. 10.1, 17.0, 23.3, 13.2,39.6,6.7 o 1 2 3 4 5 6 7 8 9 10 . ·n 12 13 14 IS 16 Ultra-violet Band Systems 0/ the Mercury Iodide Molecule. 331 o 4 5 4 4 3 5 4 4 3 5 5 3 3 2 3 5 4 4 2 4 4 3 3 3 TABU 5 Intensity Distribution (Systelll C) 5 5 3 3 3 4 4 3 3 4 4 3 1 4 4 4 3 4 3 5 I 6 7 ! ----~ .. I ! 3 i 5 I J I 3 2 5 4 3 1 ~ 4 5 J ill ! N o .., ... 3 3 3 4 o 2 00 I N cj, I c.6 01 . i 8 9 3 10 3 ~ I "'I 0>, I II 2 The separation of the isotopic heads of a given band (1/, 1/') is given by 23 1 . .1 225.6 224·4 216·9 210.~ 209.3 2C14· 0 198·2 198.4 193. 1 197·() li6 '5 182·9 16$.8 171.2 168.2 Where v t refers to the less abundant molecul~. The isotolJic separation is cal. culated fr01l1 this formula for the two isotopes 198 and 202. The maximum separation is about 5 to 6 units and is certainly measurabie for the bands n:l11ote from the origin. Examination of the spectrul11 failed to reveal an~ faitlt heads which could unlllistakably be assigned as such. They must have been marked by the considerable overlapping arising from the unresolved rotational structure and the proximity of bands due to different vibratio1lal transitions. The diffuse. ness of the bands justifies this assumption. INTERPRETATION The ultra violet emission spectra of mercury fluoride was analysed by Howell (1943) into two systems wbich were interpreted as the two components of a 'TI_2}; transition with the 2I1 interval Av being 3940 cm-1. By a comparison of this separation with the over all width of the 3p state of the Hg atom, Howell showed that the moleculat constant A (= Av) for a II electron giving lise to a 2TI state in HgF.is of the same or&r as the coupling COllstant a (= 2265) for the 6p electron giving the 6s 6p3p state of tile Hg atom. This approximate equality together with the important observation by Carnell that all the ultra violet band spectra of the halides of 2n, Cd and Hg studied by him occur near the resonance lines of the metal atom led Howell to put forward the view that the transition involved in the emission 332 K. R. Rao, M. G. Sastry and V. C. Krishnamurt' of the baud systems of these halides is atomic in nature. The doublet splitting of the 2II state should then be nearly the same in all the halide bands of any parti-cular metal atom Zn, Cd or Hg, the influence of the halogen atom being negli-gible. This feature was shown hy Howell to hold in the various halide bands for which data were available. Examining the HgI band systems C and D in the light of this view, it would appear that these systems might form the two components 2II_2:$ transition, the interval 21I 3 -2111 being equal to 3538 cms- I . t.! "2' In Table 6, the separations between the (0,0) bands of what are believed to be such analogous components in the halides hands of Zn, Cd and Hg are collected. The data are mostly tentatively suggested by Howell (lac. czl.). The value for Hg CI is confirmed recently by one of the authors (Rao, 1944). and that for HgI is from the present work. TABU 6 Hg Zn Cd F 3934 II 79 CI 3889 IllS Br I 3510 Atomic coupling 4265 386 constant There is a definite decrease in the value of the molecular constant from the . lightest Hg F to the heaviest Hg I molecule, indicating an increasing deparfure from the atomic coupling constant 4265 em-I, a feature which should be expected as the influence of the halogen atom, cannot he altogether neglected. Accurate data on the other spectra are also needed before further light can be thrown on this question. Experiments in this direction are in progress in this laboratory. ANDHRA UNIVERSIl\', GUNIUR REFERENCES Howell. 1943. 1'roc. Roy. Soc. (Lond.) .1. 182. 95· Prithesbejewa, 1932, l'hys. Z. Scwjet. 1, 189. Rao K. R., 1944. Curro Sci. 23. 279· Sastry. 1942. Proc. Nat. lnst. Sci. Indta, 8. 2&}. Seaberg. 1944. Rev. Mod. Phys •• 16. I. Wieland, 1929, Helv. Phys. Acta, 2,46 and 77-Wieland, 193:1, ZeUs. f. Phys, 76, 801 

Ultra-Violet Band Systems of the Mercury Iodide Moleculer-Part I

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Ultra-Violet Band Systems of the Mercury Iodide Moleculer-Part I

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