178
RICHARDPOMEROY AND
H.DARWIN
Vol. 6ti
KItSCkfMAh'
[CONTRIBUTION BEOM THE UNIVERSITY OF CALIPORNIA AT LOS ANGELES]
The Solubility of Sodium Iodide in Sodium Hydroxide Solutions at 20" BY RICHARD POMEROY AND H.DARWIN KIRSCHMAN
In a recent article' we have presented the resuits of a study of the solubility of potassium iodide in potassium hydroxide solutions a t 20" over the range 0 to 14.35 N in alkali. The present paper extends the study to the iodide of sodium in solutions of sodium hydroxide from 0 to 15.21 N. The results of our measurements are presented in Table I and Fig. 1. 1.80 161
0
Density grams per cc. 2.00 1.90
1
I
I
2 4 6 8 Moles of NaI per liter. Fig. 1.
1
0
Experimental Sodium iodide of c. P. grade was purified by recrystallization as the dihydrate. A highly concentrated solution of sodium hydroxide was prepared, filtered free from car-
TABLE I SoLUBILITY AND
NaOH
moles/litu
0.00 0.97 1.40 1.76 1.77 2.62 3.72 3.78 4.04 4.90 4.93 4.94 5.46 6.38 7.10 7.16 7.19 7.24 7.27 7.54 7.74 8.20 8.30 8.66 9.29 9.44 9.61 9.70 10.36 11.38 12.71 13.41 13.49 13.95 14.24 14.41 15.21
DENSITY DATAAT 20 '
NaI rnoles/liter
8.14 7.74 7.69 7.40 7.34 7.11 6.76 6.72 6.63 6.48 6.43 6.54 6.40 6.36 6.44 6.45 6.42 6.41 6.56 6.49 6.66 6.92 6.88 6.76 6.54 6.60 6.47 6.34 6.24 6.99 5.76 5.62 6.64 5.50 5.52 5.45 5.42
Denaity. g./ml.
1.910 1.888 1.881 1.876 1.871 1.872 1.860 1.856 1.856 1.865 1.858 1.870 1.870
1.885 1.905 1.908 1.912 1.908 I. 919 1.922 1.942 1,981 1.977 1.972 1.965 1.962 1.962 1.948 1.966 1.952 1.958 1.957 1.958 1.953 1.959 1.959 1.970
bonate, and crystallized as the monohydrate by cooling. The bottle containing these c r y s t a l s was warmed to produce a melt which was mixed with suitable amounts of
Equilibrium seemed to be somewhat more slowly attained than in the experiments with potassium iodide in pq-ium hydroxide but a few trials employing mechanical water and sodium iodide crystals in the equilibrium bottles. stirnng of the mixture for several hours showed satisfacThese bottles were then immersed in a water-bath at 20' tory agreement with other methods of saturation. The for from four to twelve days and shaken frequently. Por- density and solubility curves show a discontinuity at a tions were removed with pipets and diluted with water to point corresponding to 8.20 N in sodium hydroxide and suitable concentrations for analysis. The drainage error 6.92 N in sodium iodide. The solid phase in the mixtures in the use of a pipet with these rather viscous sohations with hydroxide concentrations above 8.20 was identified was corrected for by washing out and titrating the residual as anhydrous, cubic, sodium iodide. liquid in the pipet. T h e alkalinity was determined by The accuracy of results is estimated to be 1%. titration with standard sulfuric acid solution using methyl orange indicator. The iodide content was determined Summary gravimetrically as silver iodide. The density detennlnation was made by weighing a 26-ml. sample of the satuThe solubility of sodium iodide a t 20' was derated solution. These weighings were corrected for the termined in sodium hydroxide solutions from 0 buoyant effect of the air. to 15.21 N in alkali, The density and solubility
c w e r show a discontinuity at a point correspond-
Feb., 1944
THEDENSITY AND TRANSITION POINTS OF THE PARAFFIN HYDROCARBONS 179
ing to 8.20 N in sodium hydroxide and 6.92 N in sodium iodide, which point marks the transition
from the dihydrate to anhydrous sodium iodide. PASAJJENA, CALIF.
RECEIVED OCTOBER 4,1943
[ C O N T ~ ~ ~ UFROM TION THE DEPARTMENT OF CHEYISTRY, THE UNIVERSITY OF BRITISHCOLUMBIA]
The Density and Transition Points of the n-Par& Hydrocarbons BY WM.F. SEYER, RALPHF. PATTER SON^ AND JOHN L. KEAYS~ the previous article, the melting points, even when done by the method outlined by Piper, ct al., were d e c t e d by the rate of heating and the personal equation, but experience showed that the setting point was not. It could be reproduced by any worker in the Laboratory to within 0.2 to 0.1' for any one sample by observing the temperature when the first crystal formed upon slow cooling (temperature dropping less than 0.6' per minute). Hence, the Materials.-All of these hydrocarbons excepting Cl,~Hsc setting point has been used in this Laboratory for the and &Hw were synthesized in the laboratory. Samples purpose of establishing the purity of the compoundsunder of hexadecane were obtained from Messrs. Deanesly investigation. The observed setting points along with and Carelton of the Shell Oil Company, and Professor the melting and transition points are given in Table 11, Parks of Stanford University. Both samples were from where N denotes the number of carbon atoms in the chain. lots that had been carefully purified by the donors, but Equations have been developed by M o ~ l l i n ,Tea~ upon comparing the m. ps. of the two, it was found that totos,' and GarnetJ for correlating the meltlng points mth the m. p. from the former had a slightly higher value than number of carbon atoms in the parsffin hydrocarbon chain. that from the latter. The m. p. of the best material was None of the equations was found to be satisfactory over found to be 18.145and its setting point 18.3. the whole range of melting points. Moullin's equation, The nonacosane was obtained from the Bureau of which is of the form log (N 2) a bt, could be made Standards through the efforts of Dr. B. J. Mair. It had to fit the curve of melting point against carbon number, if an m. p. of 63.0"but as Piper and his co-workers' gave a one assumed discontinuities a t about N = 16 and N = 33. value of 63.4-6' it was recrystallized until the m. p. rose N here represents the number of carbon atoms in the chain to 63.5 and a and b are constants. There is also up to C d I u one The method employed for synthesizing the desired curve for the odd numbers and one for the even numbers. hydrocarbons depended upon the nature of the material Above this member, melting points of the odd and eveii available. Where alcohols served as a starting point the numbered p a r a h s fall on the same straight line. Kraft procedure was followed and where acids, the Peterson The values of the constants, a and b, obtained by the electrolytic method was utilizcd. After the usual pre- method of least squares for different sections of the curve liminary purification the hydrocarbons were treated with are given in Table I. Members lower than CsHrr, for sulfuric acid until no color formed upon the addition of the both the odd and even numbered compounds, are not acid. To remove it, the hydrocarbons were washed with included, as the deviations of observed from calculated hot water. They were then dried and recrystallized from m. ps. are too great. The recorded m. p. of C I I His~ also five to twenty times until a constant m. p. and t. p. were out of line. obtained TABLE I Tetratriacontane, the highest member so far synthesized, VACUES OF CONSTANTS a AM) b was prepared by the electrolysis of the corresponding acid which in this case was stearic. Considerable dificulty was No. of carbon atoms rang.: a b encountered in the purification of this compound. It G + CIS(even) 1.061 0.00481 could not be obtained completely colorless although it was .00410 G Cir (odd) 1.067 drastically treated with sulfuric acid and recrystallized CIS Cu (odd and even) 1.02 ,0066 from glacial acetic acid over forty times. The reason for this failure may lie in the following statement of Oldham 0.08 .o006 c a l Go and Ubbelohdc.' "Owing to the appreciable oxidation of certain liquid paraffins at 130°, it was advisable to hinder In correlating the melting points of the normal paraffin the circulation of air over the surface of the paraffin during series with numbers of carbon atoms in the chain, it w a s the purification." It may be that this hydrocarbon was attempted insofar as possible to select values obtained by oxidized a t the temperatures where purification was one set of workers. For as has been mentioned above, them. ps. obtained depend not only upon the purity of the attempted. product but also upon the m. p. technique. Further, Melting Points of the Normal Paraffin Hydrocarbons.A knowledge of the melting points of the normal paraffin workers interested in a set of values are sure to develop hydrocarbons was found to be essential for the present laboratory methods and gain experience much broader investigation. Piper,' et al., claim that the transition in scope that those who accidentally are led to make point is a more reliable index of purity than the melting measurements only on one compound. Consequently, point.' This may be true for those hydrocarbons having we have used the selected values of Deanesiy and Carletone more than twenty-six carbon atoms but for those below for the range 6-18,and our own for the range 18-34. this in the series this cannot be so, because there is either For 40,60,60 and 70 we selected the melting point given by Carothers,*Oand for 36,62,62and 64those of Gascard.l1 no - transition point or it is indistinct. As mentioned in
The density and transition point of dicetyl (CaHsa) formed the subject matter of a previous communication to this JournaLa Since then, all the even-numbered hydrocarbons, beginning with ClaHsr and ending with C U H ~have ~ , been inof the odd-numbered series. vestigated, also
-
i=
+
.
.
(1) Standard Oil Company of British Columbia Research Fellow, 1938-1939. (2) Standard Oil Company of British Columbia Research Fellow, i94i-iwa. (8) Seyer and Morris. TEISJo-NAL, 61, 1114 (1939) (4) Piper, et al., Bfochem. J . , I O , 2072 (1931). (6) Oldham and Ubbelohdc, J . Ckm. SOC.,200 (1888).
(6) Mwnin, R o c . Camb. PhiI. Soc., M.469 (1938). (7) Taakototca, Compl. rend., la,1235 (1900). (8) b o a , Van B i b k r and King, J . Chsm. Sor.. 1633 (1931). (9) Dconedy and Carleton, J . Phys. Ckm., 46, 1104 (1941). (IO) Cuothera, Hill. Kirby and J.eobrw, hn J O ~ N U , I , 6479 (1880). (11) ouarb,AW. ~irn.. u,sa2 (ieau.
