INDUSTRIAL A N D ENGINEERING CHEMISTRY
1272
tion. The oxidation was complete after passing the solution through the tower five times. Equally satisfactory results were obtained with other concentrations of ferrous sulfate solution. All these runs were made a t room temperature. Neutral solutions of ferrous sulfate gave considerable amounts of the basic sulfate, covering the catalyst, especially where the pieces touched each other or the walls of the tower. Using solutions containing the theoretical amount of acid, only little basic sulfate was formed, and this did not appear to reduce the efficiency of the process appreciably. The cata-
Vol. 15, No. 12
lyst is easily cleaned without removing it from the tower by washing with a little dilute sulfuric acid. The same lot of manganese dioxide was used for all the runs made and during these experiments showed no tendency toward becoming "poisoned" or otherwise losing its efficiency. The pyrolusite used showed on analysis the usual impurities common to the mineral-iron, silica, etc. I t is very interesting to note that, while this impure substance was wonderfully active as a catalyst, the pure material had very little action.
Analysis of Mixed Salts by Freezing Point Method'
h
$
4*
6-40
2
500 2o
c.
1920 Lautsberry and pagezpublished the results of their search for simple mixtures of molten salts suitable for steel treatment, They used sodium, calcium, and potassiumchlorides, and arrived at the following data:
700,
3o
4o
5o
~~
a freezing point of 660" There are two mixtures with this freezing point, but only one answering to the calcium analysis-namely, 56.65 per cent sodium chloride and 43.35 per cent calcium chloride. Fig. 2 shows the type of curve plot used with ternary mixtures of salts. Here the plot is in the form of a triangle with the pure salt a t each corner and various diminishing percentages represented by parallel lines a t regular distances from the corner. Thus, the top point of the triangle stands for 100 per cent potassium chloride and the line connecting the other tmo corners is zero per cent potassium chloride. 1-With sodium and The curves shown are isotherms, or lines extending through potassium the minimum various mixtures having the same freezing point. The mix~ ~ ~ " , $ ~ ~ t i ture ' ~ having ~ ~ ~thei lowest & freezing point is called the eutectic and in this plot is of practically constant sodium chloride chloride. 2-With calcium and content for a change of 30 per cent calcium and potassium
freezing point is FIG.I-FREEZING POINTCURVEOF NaC1-imum 505" C. for 72.5 per cent CaCL MIXTURFS
calcium chloride. 3-With calcium and potassium chlorides two eutectics and a maximum point were obtained. The maximum freezing point is 725" C. for 2KC1.3CaClz. The two eutectics are 608" C. with 17.5 per cent potassium chloride, and 590" C. with 60 per cent potassium chloride. 4-With potassium, sodium, and calcium chlorides two eutectics were obtained-namely, 495' C. for 70 per cent calcium chloride, 25 per cent sodium chloride, and 5 per cent potassium chloride; 530" C. for 30 per cent calcium chloride, 20 per cent sodium chloride, and 50 per cent potassium chloride. These results show in large print in the plot of ternary mixtures (Fig. 2). I n order to prepare for such analyses in plant control work, a series of salt mixtures should be prepared and analyzed and then used for freezing point determination, thus yielding a freezing point curve which will be a great time saver to the chemist or plant control man. Such plots have been prepared in the case of sodium and calcium chlorides, and mixtures of sodium, calcium, and 1 9
Received May 21, 1923. J . SOC.Chem. I n d . , 89, 37 (1920).
Ep*8,J
FIG.2-FREEZING POINTSOF MXXTURBS OF NaCl, CaCb, W
719 'G
D KCl
Let us assume the analysis of a mixture of these three salts yields the following:
INDUSTRIAL ALYDESGIYEERI_vG CHEMISTRY
December, 1923
1273
Calcium, 14.43 per cent, equivalent to 40.00 per cent CaC12; very close control can be kept on the feeding of these furnaces freezing point, 620 C. by a systematic follow-up of freezing points. The usual procedure of freezing point determination is By consulting Fig. 2 a t the proper freez$g point the mixture is found to consist of 40 per cent calcium chloride, 46 to fill a small iron crucible with molten salt mixture, suspend per cent sodium chloride, and 14 per cent potassium chloride. in it a base-metal thermocouple, and record the temperature These and similar curves are also very useful for the re- or freezing point curve on a suitable graphic instrument. verse operation-namely, the determination of freezing Just before complete solidification the couple may be withpoints of various salt mixtures, especially in connection with drawn from the salt and washed in readiness for the next the operation of the so-called fused electrolyte furnaces. A determination. O
T h e Vapor Pressures of Gasolines and Light Petroleum Naphthas' By. F. H. Rhodes and E. B. McConnell CORNELL UNIVERSITY, ITHACA, N.
Y.
has been deviseda whereby PON the vapor presA method for the exact determination of the vapor pressures of some of these errors are sure exerted by a gasoline and naphthas is described, and the vapor pressures of seueliminated. This improved gasoline or a light era1 di3erent types of gasolines and naphthas are measured. method is, however, still petroleum naphtha at or I t is shown that no general relation exists between the vapor pressubject to the error due to slightly above the ordinary sure of a gasoline and its aoerage distillation temperature or its the presence of air dissolved temperatures depend, to a density, and that the presence of air dissolved in the gasoline or in the gasoline. The results considerable extent, the loss naphtha may introduce into the uapor pressure determination an obtained by these methods, which will be incurred when error of considerable magnitude. while they may be of value the material is handled or stored, the internal pressure in estimating the pressures developed in shipping containers used for transporting the developed in shipping containers, do not give the true vapor material, the fire hazard incurred in handling the naphthas, pressures of the naphthas. and the ease with which the gasoline may be vaporized in 8 Private communication from R. P. Anderson. the carburetor of an internal combustion engine. A number of methods for the determination of the vapor pressure of gasoline have been devised, and some information on the vapor prefisures of gasolines has been published. The method commonly used for testing casinghead gasolines and blended gasolines in order to determine whether or not tliey may safely be shipped in tank cars or standard drums, has been described by the U. 8. Bureau of Explosives.' A steel bomb is partially filled with the naphtha to be tested, the bomb and its contents are heated to the temperature a t which the, determination is to be made, and the pressure within the bomb is observed. In order to decrease the error due to the expansion of the air in the space above the liquid, this space is momentarily vented to the atmosphere when the temperature of the gasoline reaches 70" F. This method is subject to several sources of error. Some of the lighter components of the gasoline may be vaporized below 70" F., and the vapors thus formed will escape when the relief valve is opened to vent the expanded air. When the bomb is heated from 70" F. to the temperature at which the vapor pressure is to be measured (90" or 100" F.), the air above the liquid tends to expand, and the increase in pressure thus developed is measured with and not differentiated from the increase due to the true vapor pressure of the gasoline. Some of the air present in solution in the original sample may be liberated when the naphtha is warmed, and tho pressure developed by this liberated air may be measured along with the true vapor pressure. No means for agitating the liquid is provided so that there is no assurance that the liquid and the vapor within the bomb are in true equilibrium with each other. A modification of this bomb
IIJ
A
' I
Received June 20, 1923. Report of Chief Inspector of Bureau of Safe Transportation of E x plosives and Other Dangerous Articles, February, 1916. 1
2
FIG. 1
