THE RIOLECULAR W E I G H T O F ORTHORHOMBIC, ~ I O S O C L I K I C , A S D PLASTIC S U L P H U R I N S X P H T H A L E K E AND P H O S P H O R U S , HY THE F R E E Z I K G - P O I K T RZETHOI)
BE' SAMUEL D. GLOSS
T h e man>- different investigations on the molecular weight of sulphur seen1 still to leave some room for question as to the
values indicated for the different varieties. Thus, in the papers of Biltz,' Raiiisay,2 Biltz and Rleyer,3 Beckmann,4 J. Hertz,' Helff ,6 Paterno and K a s i n i , ~Scliall,8and Orndorff and Terrasse,g I find only two instances in which comparison has been made between the different kinds of sulphur. Orndorff and Terrasse concliide that orthorhombic and monoclinic sulphur have the same molecular weight since there is no difference in the results obtained by the boiling-point method in carbon disulphide (B. P. 46")and in benzene (R. P. 79.6') although only the orthorhombic variety crystallizes from the first and the monoclinic from the second. Biltz also finds no difference between the orthorhombic and plastic varieties by the vapor-density method. It would seem more likely that differences might be discovered by methods apphys. Chem. 2, 920 ( 188s). 3, 67 (1889). 4, 266 (1889). 5 , So (1890). 6, 358 (1890). 12, 196 (1893.1. Rer. chem. Ges. Berlin, 21,21j3. Ibid. 23, 1704. Am. Chem. Jour. 18, 173 (1896). Zeit. Ibid. Ibid. Ibid. Ibid. Ibid.
122
Sa11111cl
n.Gloss
plicable at low temperatures than by those in\-olving a high temperature, as in all the \-apor-cletisitJ-determinations. ;iccorditigly in the following esperinients the attempt has been made to coinpare the valnes ohtaiiiecl for the several varieties in some solvent n-liicli has a low freezing-point, atid also dissolves large quantities of sulphur. Saplithalene n-as first tried, (F.P. 79.4"), and then phosplioriis (F.I]. 44.2 'I. T h e orthorhombic sulplinr was prepared bj- crystallization froin carbon disnlpliide and the iiionocliiiic from fnsion. T h e plastic was macle from the crj.stallizec1 ortliorlioiiibic in the usual manner, bj. turning the melted snlpliur into cold n.ater. This \vas dried 1 1 ~ absorbent paper, weiglied atid qiiicklj- used. T h e naplitlialene, tlie commercial article, was siiiipl?. melted and filtered. T h e mixtures were melted in a large test-tube iiiimersed in a beaker of water. TIiej- \yere allon.ed to cool slon-lj-, with coiistaiit stirring, until solidification beg-an, accompaniecl by rise of temperatiire, and tlie iiiaxiiniiiii readiiig of tlie theriiionieter n-as taken with tlie aid of a iiiagnif!.ing glass. In the observations with naplitlialene, a Beckiiiaiiii tliermoiiieter was used, gracluated to a hiiiidrecltli of a degree. In the series n.itli phosphorus a tliermonieter graduated to a tenth of a degree \\-as used. ordinarj- tliernioiiieter ga\-e tlie temperature of tlie water, n.liicli n-as kept coiistaiitly stirred. In naplitlialeiie, ortliorhonibic and tiionoclinic siilphiir dissolve reaclilJ-, although the latter seems to lea\-e a slight residue. Plastic sulphur dissolJ-es very slowly. T h e precipitated and s u b h i e d varieties dissolve so inconipletelj-, except above IOO", that they were not used. T h e freezing-point of naphthalene was cletei-miiied by tliirteen readings on the same sample, n.liicli gave resnlts from 79.250' to 7S.S", the average is 79". Several readings were taken in each deteriiiiiiatioii as slion-11 in the following table :
So. 6
So. 4 ____ ~ _ _ _ _ _______ __~____~_____~~ __ I.jS 1.34 I .6o 1.612j 1.34 1.59 1.61 1.34 1.60
s o .j
~
~
1.347j
1.6oj
1,3475
I ,G4
1.3375 I .\355 1,345
1.34
hleaii 1.616"
so.
_
_
s
_ ___
~
_
_
I .38
1.39 1.41
~
I.62
.
I.12
1
1.415 1.400 1.425
1
__-
-.
I.3W3
I ,j9'
1
-I. p O "
Tlie iiiaxiiiiiiiii T-ariations in these four series are : 0.0jjc, O . O I ; ~0 ~. 0~ 2 ~ and o.o+j' respectivelj-. A \-ariation of 0.01'in the Ioiveriiig for the solution of iiiasiinum concentration it1 this series, iiaiiiely 2 g in IOO g of soli-exit makes a difierence of 6.5 in tlie molecular weight. T h e repetitions of tlie freezingpoint, oii the same sample, also slio\v that the solution does not change with aiiy regularit>. b!- repeated heating aiid cooling. Tlie coilstant for naphthalene, 63.4)is calculatetl by \-an't Hoff's formula. T h e iiiolecular weights obtained in these four experiments, see Table KO.I , are 28; a i d 271 for the orthorlionibic, 253 for the plastic, and 2 9 2 for the moiiocliiiic. These results are practicall>- identical for the three varieties of siilpli\ir at coiiceiitrations of only oiie aiitl two percent. The values of Oriidorff and Terrasse for coiiceiitratioiis hetween one percent atid ti\-o and four-tenths percent, lie between 233 and 251. Hertz's valoe for two aiid four-tenths percent is 262.
I n as iiiuch as plastic and monoclinic sulphur cliaiigc rapid!- at about IOO", it is possible that the change ma!- take place before the snlistances go into solution at the freezing-point of iiaphthaleiie, ( j 9 " : . I t \vas thought that the coinparison niight be iiiore decisive in a soli-eiit of loiver freezing-point, aiid so phosphorus was nest triecl, (F. P. 44'). In these espei-iments the fiisiniis were niade under water instead of iii an atmosphere of carbon dioxide, as in Helff's experiments. I n weighing tlie sample of phosphorus it
424
Snmzicl D. GZoss
was first dried by absorbent paper, and then weighed in a beaker of water, the weight of which had been previously determined. On repeated heating and cooliiig of the mixture of phosphorus and sulphur, a white milky color is given to the water above it, evidently due to the separation of sulpliur, and an evolution of hydrogen sulphide takes place. T h a t neither of these reactions takes place rapidly enough to interfere appreciably with the results was s1ion.n by repetition on the same sample with a considerable interval of time. In calculating the results with sulphur in phosphorus, the coiistaiit used for phosphorus is the one given by van 't Hoff's formula, iiaiiiely 384. Orthorhoinbic and inonoclinic sulphur are readily soluble in phosphorus. Plastic is slowly soluble and seems to leave a slight undissolved residue, like precipitated sulphur. I n this series the plan was adopted of dissolving first eleven percent of sulphur, which brought the freezing-point down to about 2 7 O , when two portions of three percent each were added at this low temperature. In the cases of nioiiocliiiic and plastic sulphur, againple of the sulphur was kept in a tube along side of the one containing the mixture. I t was thus seen that the sample did not change during the interval and at the temperature of the solution. Care was taken that the temperature during solution should not rise tilore than four or five degrees above the freezing-point. T h e freezing-point of the phosphoros alone was 44. I '. T h e eleven percent portions of orthorhombic and inonoclinic sulphur give for the molecular weight the following values See Table I1 : -
Orthorhombic
Jlotiocliiiic ~
255 255 2 64 262 259 253 260
--
259 average
1
I
255 26 I 26 j 260
-260 average
These resiilts shon. no difference in the molecalar weight of ortliorlionibic and iiioiiocliiiic sulplitlr as iiiclicated by the eleven percent portions dissolved in plios~ihc~rus. T h e tliree percent additions give the following 1.alues : First tliree percetit additioiis : Ort liorhombi c ..
-.
~
~
3Ionocliiiic ~
_
3\30 300 316
I
-_
i
-
_
_
Plastic
_
_
_
~
~
~
.~ ~~~
~
~
~
~
_
_
_
_
3,!9
31 I
333
!
281
32 0
I
317
~
~
~-
__
31 I
329
Second three percent additions : Orthorhotnhic
3Ionocliiiic
~ - _ _ _ _ ~ . ~ _ _. . . _ -~~~~ - ~ ~ ~~ . _ _ ~ ~ _ ~ _ _ _ _ _ ~ _ -_ ~ _ _ _ _ _ _ ~ _ ~ ~ ~~
~~~
~
~~~
3.56 274
307
2s I __
~
~~~
~~
32 0 _ 1 - -
,733 .2i5
__
305 333 T h e axwage of the first and second portioiis is, for ortliorliom1,ic 31I , for nioiioclinic 3 2 2 . T h e oiie plastic gives 329. These results with the three perceiit adclitioiis are higher than any of Helff's results. The!. cannot lie interpreted as indicating. an!. difference in the inolecnlar xveiglit of the three kinds of sulpliur, a - e n at so low a temperature as 2 0 " to 2 j3. T.AI~I,F: 1'
'9 20 21 22
23
24 27
1s
25 26 2s 22
23
24 27 2. i
26
2'5
29 22
23 24 2;
25 26
The conclusion from this entire series of esperiinents is, tliat 110 difference is cstnblislied hetn-een the niolecular weights of ortliorliombic, iiionocliiiic, and plastic sitlphitr clissol\-ed in nnphtlialene or in phospliorus: This work \vas done in the clieinicnl lalioratorj- of S o r t h western Universit!.. Bs'nrzsfoir, Ili..2 1 1 ( ~rLiqLq ~,~,
