HYDRATED SALTS FOR F R E E Z I N G POINT METHOD
1439
I n conclusion, I wish t o record my appreciation of a grant from the trustees of the Elizabeth Thonipson Science Research Fund, which helped to defray the expenses incurred in carrying on this work. CHEMICALLARORATORY, SYRACCSE USIVERSITY, Syracuse, N. 1'.
[C O N T R I B U T I O S S
HAVEMEYER L.4BORATORIEs UNIVERSITY.No. 1 4 2 1 .
F R O M THE
O F COLUMBIA
MOLTEN HYDRATED SALTS A S SOLVENTS FOR THE FREEZING POINT METHOD 11. BY J LIVINGSTON R MORGAK A N D F. T. OWEN.
I n a recent paper' Morgan and Benson have shown that the molten hydrated salts CaCl,.6H,O,LiNO,.~H,O, and Na,CrO,. 1oH,0, when used as solvents for the freezing point method, lead to molecular weights for the dissolved substances which are similar to those obtained when water is the solvent, except that when the substance added has an ion in common with the molten hydrated salt, its ionization is prevented either wholly or in part. And when the ions of the dissolved substance are different from those of the solvent, its ionization is apparently unaffected, the molecular weights calculated, not differing materially from those observed in water solutions. I n this investigation three other molten hydrated salts, Ca(N0,),.4H,O, Zn(N0,).3H20, and Mn(N0,),.3H,O, h a r e been studied as solvents. T h e apparatus employed was the one already described by Morgan and Benson, except that a Beckmann thermometer, reading to o O . 0 1 , and set by aid of a normal thermometer, reading to o O . 0 2 , was used throughout. T h e depressions recorded are each the average of three determinations, agreeing among themselves to o O . 0 2 . Just as with the other salts the separation of the solid phase was induced by infection with a crystal of the pure solvent; and the overcooling was kept below I O to avoid the necessity of correcting for the fraction of solvent separating as a solid phase. Determination of the Constants. For Ca(NO,),.qH,O the latent heat of fusion is 33.49 gram-calories per gram, according to Pickering', so that the freezing point constant can be o.ozTZ calculated directly from the relation K = , where T is the ab~
W
solute freezing point of the pure solvent, w its latent heat of fusion for I g. a t that temperature, and K the depression of the freezing point in degrees, caused by the presence of I mol. of dissolved substance in IOO g. of the solvent. Since the freezing point of molten Ca(NO,),.qH,O, as determined b y us, is 42O.31,we have This Journal, 29, 1168-75, 1907. See Landolt-Bornstein-Meyerhoffer.
Tabellen.
Third ed., p. 470.
I440
J . LIVINGSTON R . M O R G A N A N D F. T. O W E S
K = 0.~ .02 ( 2 7 3
-12.31 )' = j 9 0 . 4 1 . 33.49 For neither Zn(N0,),.3H,O, nor h f n ( xO,),.3H,O could the latent
heat of fusion be fourid in the literature, hence it was necessary to determine the values of K by direct observation of the freezing point depressions. For this purpose ammonium nitrate was used as the solute, for it dissolved readily in both solvents, arid the work of Uorgari and Benson, with molten Li?u'0,.3H,O as solvent, showed it to possess a normal niolecular weight when the solvent contained NO, inn, i. E . , showed that under these circumstances it dissolved in practically the uti-ionized state. T h e freezing point depressions observed for solution of ammonium nitrate, of known strength, in these two solvents are given in Tables I and 11, below, the value of K i n each case being the depression which would be caused by the preserice of I mol. ( s o g ) of ammonium nitrate in IOO g . of the solvent, as calculated by the proportion 8o:K::g. per I O O : ~ . IS Z S ( N ~ , ) , . ~ H ~AO S SOLVXST.F. 1'. == 44O.o;.
I. f l i i r m m i w i i ATitvntc, (.V .= Go j. g. .UH4N0,; per
IOO
1.470
A2
K3
1.0jI
5s.;
2.52s
1.S30
3.793 5.249
2,773 3.910
57.9 5s. 5 59.6 .\verage
jS".6 0.02T'
Using this average value of K , j 8 O . 6 , in therelation I; =-
~
ii'
, and
solving for w , me find the latent heat of fusion of Zn(SO,j,.gH,O to be 34.3 gram-calories per gram at its freezing point 44O.07. F.I-'.= 3 5 O . s ~ . IN M N ( X O ~ ) ~ . ~ASH SOLVENT. ~O I . Ainmoitiuiiz A'ilmtc (171= So). per
g. ",NOl
IOO
I .063
I;
13
0.ssz
1.492
1.273
3.0j2
2.573
66.4 6S.3 67.4
Ayerage
6jO.4
Using this average value of K , 6 7 O . 4 , in K = 0 ' 0 2 T 1, and solving for W
w , we find the latent heat of fusion of I g. of M n ( S 0 , j 2 . 3 H , 0 to be 28.09 gram-calories, a t its freezing point, 34.81.
Molecular Weights in Solution. TK CA(N0,),.4H20 AS S o ~ v ~ i i TK.
= 59O.4. F. 1'. = 4 2 O . 3 1
IZZ. Cren ( M = 6 0 ) . g. per
ICO
0.9S6S I .9030 2.9900
10
3I
1.920
j6. j js. 9
3.071
57.9
I .0$3
1441
HYDRATBD SALTS FOR FREEZING POINT I\IETHOD
ZV. Amvzoniirnt Nitvate (JZ= 8 0 ) . g. per I W
2.280 4.789 5.644 V. Glycol ( M = 62). 0.9249 I .8660 2.8080 3.6640 VI. Acelic Acid ( M = 60). 1.092 2.138 3.497
A0
hf
1.702 3.577 4.311
79.6 79.5 77.8
0.884 1.779 2.730 3.588
62.2
62.3 61.1 60.7
60.2 63.7 69.I K = 5P.6. F. P. = 44O.07. IN ZN(NO~).~H~O AS SOLVENT. VZL E t h y l Alcohol (.%f = 46). 1.083 45.5 0.8397 1.728 45.8 1.3553 VZll. Methyl Alcohol ( M = 32). 33.2 0.843 0.4776 0.8198 34.9 1.375 1.906 1.141 35.1 1.461 35.I 2.440 1.814 3.030 35.I 35.0 2.445 4.103 IA'. Acetic A d ( M = 60). 60.3 0.5663 0.550 62.8 1.188 1.273 2.236 64.9 2.475 3.681 67.5 3.'97 A.' Acetone (JZ= 5 8 ) . 0.828 59.7 0.8435 64.4 1.578 1.7344 2.626 65.3 2.358 66.4 3.119 3.536 XZ. Foimnnride ( M = 4 5 ) . 1.442 55.1 I.357 46.I 3.195 2.514 3.026 4.I80 42.4 Ai% ZJo-b@~~ZAZCO~OZ ( M=74). I,007 77.9 0.757 1.611 2.131 77.5 F. P. = 34'.81. IN MN(NO,),.~H,O AS SOLVENT. K = 67'4. X Z Z L Glycol ( M = 62). 60.0 0.8350 0.938 I 358 1.641 59.5 ._ 2.516 57.3 2.893 58.2 3.395 3.929 XZV. E t h y l Alcohol (AT= 4 6 ) . 58.2 0.6322 0.732 1.448 53.5 1.149 52.6 2.793 2.179 \?.ZOO 50.9 4.240 I .078 1.995 3.006
~
I442
S A M U R L A . TUCKER
-1-r . i ~ ~ , i h ~~ y l i 7.
g. p e r
s r
~( M~== .h7 z ~~.
i i
11
0 .j 6 j j
1. '49
33.2
1.124 I.Sj j
2.225 3 . 57 5 4.j20
31.4
100
2.304 TZ. G~JC(,~ oz (
.v
-= 9 2 ) . 0.7927 2.062 3.395 X l ' f f . ,-lc(-/i(--4citi (111 = 6 0 ) . 0. j902 I .24j
2.593
35.0 35.9
0.60j
ss.0
I. 702
3.25s
81.7 69.6
0.640 1.343 2.651
62.2 62.6 66.0
1.6j6 2.356 3 5i4
67.2 66. j 69.6
X1,'ZZL I 5 r a (17Z = 60). 1.6;~ 2.jj2
3.692
I t will be observed that tlie general trend of the molecular weights determined here is similar to that of those determined in CaC1,.6H20, LiN0,.3H,O, and Sa,CrO,. 1oH,0, except that i n the cases of ethyl alcohol and glycerol in Mii(iLI03),.3H,0 (Tables XIVancl X V I ) ,and forinamide in Zn( N 0 3 ) ? . 3 H , 0 (Table XZ) the molecular weights show a decided decrease with increased coiicentration. As soon a s sufficient data of this sort are at hand, a quantitative study of the thermal relations of these solutions will be macle, in order, if possible, to test the effect of the heat of dilution upon the molecular weight, as calculated by the freezing point law, the possible effect of which has already been sketched by hlorgan and Bensonl.
Summary. T h e results of this work may be summarized as follows: I. T h e freezing point constantsof molten Ca( SO3),.4H,O, Zn(NO,),.3H,O, and Mn(N03),.3H,0 are respectively: .59'.4(F. P. =42'.31); 58'.6(F. P.= 44'.07), and 67".4(F. P. = 3 4 O . 8 1 ) . 2. T h e heats of fusion for I g. each of Zn(X03),.3H,0 and Mn(Pu'O,),.gH,O, as calculated from the experimentally determined valuesofK, and the relntionw =o 027''- , are respectively 34.3 gram-calK ories at freezing point, 44O.07, and 28.09 gram-calories at the freezing point, 3 4 . O 8 1 . LABORATORY O F PHPSlCAL CHEMISTRS.
August, 1907. [CONTRIBUTION FROM THE
HAVEMEYER LABORATORIES O F COLUMBIA No. 1431.
C-SIVERSITY,
PLATINUM RESISTANCE FURNACE FOR MELTING POINTS AND COMBUSTIONS. By SAMIUEL A
'rLTCKER
Keceived J u n e 28, 1907.
T h e small furnace here described was the outcome of some work in Loc cit.
