April, 1928
INDUSTRIAL AND ENGINEERING CHEMISTRY
distillations this difference is negligible. If any distillate enters the manometer it will enter the large chamber, and will not interfere with the reading of the column. No stopcock is necessary in connecting the manometer to a system. It can be connected directly by attaching a rubber hose to the tapered tube, which is bent a t a right angle. The absence of a stopcock makes the manometer
383
very inexpensive. Including the labor of construction and the price of the glass tubing and mercury, the cost of the apparatus does not exceed $2.00. For this reason it is possible to use it in classes of general organic chemistry as well as by research workers in industrial and educational institutions. The glass blowing was done by E. F. Grienke of this university.
Solubility of Paraffin W a x in Pure Hydrocarbons' Paul Weber and H. L. Dunlap SCHOOL
OF
MINESA N D METALLURGY, ROLLA,M O .
ERY few data are available in the literature on the solubility of solid paraffins in the liquid hydrocarbons of lower molecular weight. Sakhanov and Vasil'ev2 determined the solubility of solid paraffins and the solidifying temperatures of materials containing them. The solvents used were liquid paraffins, benzene, machine oil, and acetic acid. They found that the solubilities increased rather rapidly with rise of temperature. For any particular solvent the solubility is greater the lower the melting point of the paraffin, and for any paraffin the solubility decreases wit'h the increasing density of the solvent. Sakhanov3 determined the solubilit'y of paraffin in various gasolines, kerosene, solar oil, paraffin oil, fuel oil, benzene, alcohol, and acetic acid. Sullivan, McGill, and French4 determined the solubility of closely fractionated paraffin wax of various petroleum fract'ions. The following conclusions were drawn from this work:
V
1-The solubility of paraffin waxes increases as the melting point of the wax decreases. 2-The solubility of paraffin waxes in petroleum oil decreases with increasing viscosity of solvent. 3-Differences in solubility due to differences in the melting point of the wax, or to variations in the viscosity of the solvent, decrease with decreasing temperature.
The present authors determined the solubility of a fairly pure paraffin in the pure lower molecular-weight hydrocarbons in order to find out if any relationship existed between the decreasing solubility and the increased molecular weight of the solvent hydrocarbon. Preparation and Purification of Solid and Liquid Alkanes
SOLID PARAFFIX-The solid hydrocarbon was obtained from a sample of refined paraffin by careful recrystallization three times from benzene, the sample used being about 25 per cent of the original amount. That part which first crystallized from the benzene was taken for the next recrystallization each time. The last traces of benzene were removed by distillation under reduced pressure with a fine stream of air bubbling through the molten paraffin. This product undoubtedly contains several constituents, but as no purer products could be obtained, it was used for the comparative figures. The melting point of the paraffin was 56" C., and the density 0.775 a t 20"/4" C. LIQUIDHYDROCARBOKS-The liquid hydrocarbons were n-pent,ane, n-hexane, n-heptane, n-octane, and isodecane. The pentane was secured by a careful fractionation of natural gasoline. The heptane was obtained from the Eastman Received November 4, 1927. X e f f y a n o e Khozyaisfuo, 6, 820 (1924). * Petroleum, Z.,21, 735 (1926). 4 Ind. Eng. Cliem., 19, 1042 (1927). 1
2
Kodak Company and refractioned. The others were prepared from alcohols using methods for synthesis suggested by the Eastman Kodak Company-namely, the Wiirtz reaction. These hydrocarbons, after treatment with cold sulfuric acid, washing with sodium carbonate solution, drying over metallic sodium and the final distillation, gave the constants indicated in Table I as compared with those given in the International Critical Tables.
a
Table I-Constants of Liquid Hydrocarbons BOILING POINT SPECIFIC GRAVITY HYDROCARBON Found I. C. T. (2Oo/4O C.) 0 c. OC. Found I.C.T. 36.1-36.3 36.2 0.631 +Pentane 0.631 68.9-69.2 n-Hexane 69.0 0.661 0.660 98.2-98.4 98.4 0.684 0.684 n-Heptane 124.5-124.6 124.6 n-Octane 0.706" 0.707" Isodecane 159.8-160.1 160.0 0.721 0.722 Temperature 15'/4' C.
Solubility Determinations
APPARATUS-Ade Khotinsky thermostat with which temperature could be regulated to one-tenth of a degree was used for the bath. By using a strong salt solution and placing the thermostat in a cold room, the lower temperatures were easily maintained. Receptacles for the solutions consisted of ground-glass-stoppered wash bottles to which condensers had been sealede6 These flasks, with their condensers, were attached to a frame, which was rotated almost a quarter turn in the bath by an arm attached to a motor-driven wheel. PROCEDURE-ApprOXimately 200 cc. of solvent were placed in the flask and then solid paraffin was added until a slight excess remained undissolved at the temperature at which the solubility was to be determined. At least 5 hours were allowed for equilibrium to be reached before the first sample was taken. The flasks were then raised out of the bath, warmed to dissolve some of the excess paraffin, replaced in the thermostat, and the second sample taken after a minimum of 5 hours. All determinations were discarded that did not check within 0.1 per cent. The samples were placed in 50-cc. glass-stoppered weighing bottles to eliminate loss of solvent by evaporation before weighing. The solvents were then evaporated in a closed vessel (reduced pressure for isodecane) until the paraffin residue gave a constant weight. This method was used for each of the solvents with known weights of paraffin, and the exact procedures in which the paraffin could be recovered were used for the unknown samples. The melting points of the paraffin residues checked the original melting points within 1" C. EXPERIMENTAL DATA-The solubility of the solid paraffi in the liquid hydrocarbons is calculated and recorded as 5
Weber and Dunlap, Ind. Eng. Chem., 19, 481 (1927).
INDUSTRIAL AND ENGINEERING CHEMISTRY
384
grams paraffin per 100 cc. solvent and also as grams solid paraffin per mol of solvent. (Tables I1 and 111) Data for solubilities are given to two decimal places only. The relation between solubility and carbon content of the solvent is shown in Figure 1. Slight variations in the amounts of excess solid paraffin in the flask alter the solubility data. Thus the figures given may be considered as fairly close for the paraffin used. More exact data could be obtained only by the use of a solid paraffin which contained only one individual hydrocarbon. The relative solubilities for a pure paraffin in these solvents would undoubtedly be in the same order as that found in this work.
Table 11-Solubility TEMPERA-PENTURE 0
TANE
VOl. 20, No. 4
Data-Grams
Paraffin per 100 cc. Solvent HEPOcIso-
HEXANE
TANE
TANE
DECANE
2.77 3.69 4.81 6.07 8.31 16.23
1.37 2.18 3.55 5.06 7.18 14.36
0.99 1.69 2.90 4.24 5.93 11.66
0.94 1.44 2.74 4.9s 9.17
(1.
0 5 10 15 20 25
...
5.11 6.94 9.53 17.16
Table 111-Solubility TEMPERAPENTURE
TANE
0 5 10 15 20 25
5.83 7.92 10.87 19.48
c.
... ...
...
Data-Grams Paraffin per Mol Solvent HEXHEPOCIsoANE
TANE
TANE
3.61 4.81 6.28 7.91 10.83 21.33
2.01 3.22 5.23 7.48 10.57 21.06
1.60 2.73 4.67 6.84 9.58 18.81
DECANE
...
1.84 2.84 5.40 9.80 18.03
Summary of Data
The solubility of a solid paraffin in hydrocarbons of low molecular weight increases rapidly with rise of temperature. The solubility increases from that of isodecane to that of pentane. The increase in solubility with rise of temperature is more rapid with the higher molecular-weight solvent. This can be seen by dividing the solubilities a t 10" C. into the solubility a t 25" C., the ratio being 2.3, 3.8, 4.0, 3.9, and 6.6, respectively, for pentane, hexane, heptane, octane, and isodecane; I n Table 111, except for the first three sets of data for octane and isodecane, the data run fairly constant. This indicates that the mol ratios of solvents to solute may be constant, and that we have in each case a definite number of molecules of solvent associated with a molecule of solute.
Some Azo Dyes Soluble in Non-Aqueous Solvents' Clarence E. May and Herschel Hunt INDIANA UNIVERSITY, BLOOMINOTON,IND.
IL-SOLUBLE dyes have been used for years in coloring fancy candles, oleomargarine, floor wax, shoe polish, ethyl gasoline, and plates for radio photography. One outstanding oil-soluble dye is the antiseptic oil scarlet used in medicine. This dye is used either as an ointment, a solution of the dye in paraffin, or a solution of the sulfonic acid derivative in water as an antiseptic and an aid in the promotion of granulation in wounds that do not heal readily. The authors have made and studied a number of dyes which they have been unable to find in the literature. Each new dye has been given a short name which has been selected on account of the color, the relation of the dye to some other dye, or some other point of interest. This work included the study of thirty dyes each of which was soluble in non-aqueous solvents. None of the dyes showed an appreciable solubility in water. Table I shows the dyes made, the intermediates used, and the melting points of the dyes.
0
Preparation of Dyes
ANILIXEYELLOWG(C1gH1,N8)-A solution of 10 grams of 2-naphthylamine in 20 grams of c. P. HCl and 200 cc. HzO was made, cooled and diazotized to the point where, on the addition of a dilute NaONO solution, a permanent pale blue color remained on the KI-starch paper. The diazo solution was then poured into a solution of 9 grams of dimethyl1
Received November 19, 1927.
aniline in 200 cc. HzO containing enough HCl to show a free mineral acidity in the mixture. After standing a few hours, sufficient sodium acetate was added to destroy the free mineral acidity. There resulted 11 grams of greenish yellow substance showing the following analysis: 0.2000 gram substance gave 0.5770 gram COZ and 0.0930 gram HzO Found: C = 78.68%; H = 5.48%. Theory: C = 78.54%; H = 5.18%
Azo COCCINERR(ClgHl~NzO)-Commercial xylidine (5 grams) was dissolved in 20 grams c. P. HC1 and 200 cc. HzO cooled to 15" C. This solution was diazotized in the usual way and poured into a solution of 6 grams 1-naphthol in 18 grams NaOH and 300 cc. HzO. After standing a day, 8.0 grams of dark red powder, showing the following analysis, resulted : 0.2027 gram substance gave 0.5810 gram COZand 0.1047 gram H2O Found: C = 78.16%; H = 5.81%;. Theory: C = 78.26%; H = 5.597'30
BENZIDINEBRom(C2~H20N402)-Thetetrazotization of 5 grams benzidine in 200 cc. H 2 0 and 30 grams c. P. HC1 was carried out a t 10" C. The tetrazo solution was poured into a solution of 4 grams 1-naphthol, 2.4 grams phenol, and 20 grams NaOH in 200 cc. HzO. After standing, 8 grams of black powder, showing the following analysis, were obtained: 0.2089 gram substance gave 0.5784 gram COn and 0.0851 gram Ha0
