INDUSTRIAL A N D ENGINEERING CHEMISTRY
September, 1923
combustion also increases a t the expense of the partial oxidation products. The opposite is true of the lower temperatures. Therefore, the proportion of complete combustion is not dependent upon the ratio of V ~ 0 to 6 vzo4, but upon some other factor such as the activation of the reacting substances. The reaction velocity of complete combustion apparently increases more rapidly than the reaction velocity of partial oxidation with increase in the temperature above a certain value. Again, if ratios greater than 14:l are used, with the temperature fixed, say, at 400' C., the proportion of complete combustion products to partial oxidation products is not markedly increased. With these ratios the catalyst is almost entirely VZOS, and for this reason the ratio of VZOS to Vz04 appears to have little effect upon the relative amounts of the different kinds of products. The productivity of the catalyst, whether composed of oxides of a single metal or of several metals, seems to be a function of some undetermined property other than the mere activation of the oxygen by the dissociation of the oxide. It does not seem to depend on the crystal structure of the oxides as the degree of oxidation of the catalyst does not alter its specific effect. Apparently, however, there is
967
a close relation between the crystal structures and dimensions of the metal atom and those of the organic compound and this specific catalytic action, the degree of oxidation of the catalyst a t the end of the reaction being merely a result,of the conditions obtaining in the system. As the complexity and instability of the aromatic molecule increase, there appears to be a greater number of productive catalysts which yield partial oxidation products. The benzene molecule, being the most simple and stable, is partially oxidized only by oxides of vanadium, although mixtures of oxides, which alone do not give partial oxidation products of benzene, act in a similar manner. As yet there is no certain explanation of this peculiar action of mixed oxides. I n the oxidation of naphthalene, anthracene, and the methyl benzenes a progressive increase in the number of catalysts which will produce partial oxidation products is noted. It is hoped that this rather restricted resume of catalytic oxidation of aromatic compounds will excite more extended interest, and that by a combination of the study of the atomic structure of catalysts and organic compounds, together with further studies of the specific action of catalysts, a clear path may be hewn through the confusing tangle now existent.
Solubility of Nickel Sulfate by Floating Equilibrium Method' By F. C. Vilbrandt and J. A. Bender UNIVERSITY OF NORTH CAROLINA, CHAPELHILL,N. C.
given float, the weight of HE application of The paper presents the application of the floating equilibrium solute in an unknown soluthe principle of floatmethod for the determination of the solubility of the various hydrates tion can be found by bringing equilibrium to of nickel sulfate. The method consists in the determination of the ing the solution to the same the determination of the quantity of water required to bring a solution saturated with the salt density as the calibrated solubility of the various at a definite temperature to the same concentration as a gravimetrifloat at the calibration temhydrates of nickel sulfate cally standardized solution of nickel sulfate. the concentration of the perature and then multiis a modification of the latter determined by the condition of floating equilibrium of a glass plying the weight of the principle as set forth by float calibrated for the particular solution. resulting equilibrium soluRichards and Shipley12 apA description of the thermostats, thermoregulators, and solution tion by that factor which plied to precision therapparatus is set forth. Data obtained show a close agreement with has been determined from mometry. They used variresults obtained gravimetrically. The results are usually slightly the calibration of the float. ous concentrations of salts higher by the floating equilibrium method than by the gravimetric From the weight of the to affect equilibrium for methods. original solutionythe weight noting accurate temperaof the solvent added, and tures. Lamb and Lee3utilize somewhat the same principle in measuring the density of the factor for the float, the concentration for the unknown various solutions to an exceedingly high degree of accuracy, solution can be easily calculated. The actual density of the float, whether greater or less by measuring the weights and the amount of current sent through an electromagnet that will cause a 250-ml. inverted than that of the solutions to be studied, does not materially flask in which an iron rod is sealed to sink in the solution affect the calculations. When the density of the float is less being studied. The application of floating equilibrium for than the solutions to be analyzed, solvent will always necesthe determination of the solubility of lead acetate was used sarily be added to the unknown samples to bring them to by Dundon and H e n d e r ~ o n . ~ the density of the float. If the density of the float is greater The application of the principle suggested by Dundon than that of the solution to be analyzed, it becomes necessary and Henderson has been carried on in this work on the hy- to evaporate the solvent from the solution until it and the drates of nickel sulfate, and the method of application and float are in equilibrium. The value for solvent added then calculation of data are made easier by the development of becomes a negative value instead of a positive one, as in the a simple formula. I n this method is determined the weight case above. The purpose of the work herein described is to study the of solvent which will bring a solution of unknown concentration to the concentration in which a glass float calibrated applicability of the floating equilibrium method (1) to the a t an arbitrary temperature will remain in equilibrium. analysis of the concentration of solutions of nickel sulfate, Assuming the percentage of solid in equilibrium with a and (2) to the determination of the solubility of the various given solvent to be constant a t a fixed temperature for a hydrates of nickel sulfate.
T
1 2
8 4
Received March 28, 1923. J, A m . Chem. Soc., 34, 599 (1912); 36, 1 (1914). Ibid.. 35. 1666 11913). Ibzd.; 44; 1197 (1922). ~I
PREPARATION OF THE PURE SALT A large quantity of the best grade of C. P. nickel sulfate was recrystallized from distilled water three times, this
968
INDUSTRIAL A N D ENGINEERING CHEMISTRY
material alone being used for stock in the determinations, no residues from the determinations being used over again. The stock salt was the pale green, rhombic crystals of the formula NiS04.7Hz0. Tests for impurities showed no iron or hydrogen sulfide metals, and but minute traces of chloride and cobalt. The three hydrates of nickel sulfate were made by recrystallization of the stock sulfate a t 25" C. for the heptahydrate (green), 40" C. for the hexahydrate (blue), and 70" C . for the hexahydrate (green). By carefully maintaining the temperatures until crystallization set in, then rapidly swinging off the mother liquor, a fine, stable grade of each of the hydrates was obtained, which underwent no noticeable change in color or hydration on standing in stoppered bottles. Analysis of the crystals for nickel by the dimethylglyoxime method proved their purity and formula as to nickel content. On the stock nickel sulfate heptahydrate the percentages of nickel were calculated from the analyses as 20.42, 20.90, 20.85. Calculation of the same from the formula gives 20.89 per cent. Analyses of the blue monoclinic and green hexahydrate for nickel content gave 22.42, 22.30, and 22.31 per cent while the theoretical quantity present should be 22.326 per cent. A hollow, pear-shaped glass float, with a fine capillary a t one end, occupying, a volume of about 1.5 to 2.0 cc. was made from ordinary, small, soft-glass test tubes. A solution of nickel sulfate approximately saturated a t 0" C. was prepared, and by the addition of mercury through the capillary the float was brought to about the same density as the solution a t room temperature. The capillary was then sealed off. The float used in these determinations was made about four weeks before the calibration, thus avoiding any large error due to slow contraction of the glass on aging. A subsequent calibration a t the conclusion of the solubility determinations showed that no perceptible change in volume had taken place after the f i s t calibration. The determination of the exact concentration of the solution having the same density as the float was conducted as follows: A solution of nickel sulfate saturated a t room temperature or below was placed in an 8-inch test tube with the glass stirrer and float. This apparatus was then put into the thermostat regulated a t 25" C. Water was then added with constant stirring until floating equilibriumthat condition of the float when it remains suspended, or nearly so, in the body of the liquid-was reached. Samples of five different solutions of nickel sulfate brought to the same density as that of the float a t 25" C. and analyzed for nickel by the dimethylglyoxime m e t h ~ dgave , ~ the following results in grams nickel sulfate (anhydrous) per gram of water: 0.30259, 0.30755, 0.30686, 0.30304, and 0.30250. The mean of these five values-viz., 0.30451-is taken as the weight of anhydrous nickel sulfate which when dissolved in 1 gram of water gives a solution with a density equal to that of the float at 25.00" C. APPARATUS AND METHOD A 40-liter thermostat was regulated a t 25" C. to within 0.01 degree by a large toluene regulator. I n this thermostat the solutions were maintained a t the same floating equilibrium temperature a t which the float was calibrated. A 10-liter thermostat, fitted up with a heating unit and relay regulated to maintain any temperature to within 0.01 degree by a toluene regulator and stirring device, was used for saturating solutions at a definite temperature. The agitators for the saturation flask were motor-driven. The thermometers used were carefully calibrated. The solubilities of the various hydrates were determined by enclosing an excess of the hydrate with boiled distilled 6 Griffin, "Technical Methods of Analysis," McGraw-Rill Co.,N e w York, lSP1, p. 121.
Vol. 15, No. 9
water in a 250-cc. flask fitted with a rubber stopper through which passed a stirring device driven by an electrfc motor. This apparatus was immersed in the 10-liter thermostat regulated at first a t a temperature 2 or 3 degrees above the temperature a t which a Saturated solution was desired. Preliminary experiments having shown that equilibrium was reached in about 12 hours, the solutions were stirred for that time to insure saturation. The temperature was then dropped to the desired temperature and held a t this point for 12 hours. When it was desired to filter the solution, a piece of glass tubing with a small bulb blown near the end, the bulb packed with cotton and glass wool to serve as a filter, was substituted for the stirrer. The other end of the tube passed into a clean, dried tube, in which the solution was to be weighed, The solubility flask was also fitted with a suction tube, and by applying suction the solution was filtered and withdrawn from the flask into the solubility tube without having been for an instant removed from the bath. I n making the determination, the stoppered test tube into which the sample was drawn was first weighed with the glass stirrer and calibrated float. After the sample had been drawn into this apparatus a t the proper temperature, the tube with its stopper, stirrer, float, and solution were reweighed-proper drying and temperature precautions having been taken. To this arrangement in the 25" C . bath, water was added from a buret with stirring until floating equilibrium was reached. The end point was that point a t which the float would remain suspended in the solution. If the end point was passed, air was blown gently over the solution until sufficient evaporation took place to cause the float to rise, when water was again added to reach the end point. It was possible by this means to determine the concentration of a solution of nickel sulfate saturated a t any temperature by determining the amount of water required to bring the solution to the same density as the float. The weigh of water added to or evaporated from the body of the s a t urated liquid previously weighed, was a measure of the concentration of the original solution, and the weight of nickel sulfate per gram of water was calculated as follows: Let G equal the weight of nickel sulfate per gram of water a t 25" C., and WI the weight of 1 cc. of water. Then G/WI equals concentration of standard solution a t 25" C. At another temperature and condition of saturation, let x equal number of grams of nickel sulfate dissolved in Wzgrams of water, or the concentration of the solution equals x/Wz. If total weight of solution is A , then WZ= A - x. x / W z may be made equal to G/WIby adding more solvent to or allowing evaporation from the solution x/Wz until floating equilibrium is attained with the float. WSis weight of water added to or allowed to evaporate from the solution. X G Theref ore
W,+w,'iK
Wz~.= ( A - X )
Since Then
G
f z=
(A
- x; + W8
Or
To determine the concentration of the solution in terms of anhydrous nickel sulfate per 100 grams solvent, the formula becomes: 1 s or lOOx Wa (A X)
-
Substituting in the values for x: Y =
100 A
W12( A + Ws)
- Wi + GI ( A + Ws)
Since the calibration of the float determines the value of G and W I ,the calculation of results resolves itself into substituting G in the above formula the value for which, when once Wi GI'
+
INDUSTRIAL A N D ENGINEERING CHEMISTRY
September, 1923
determined for the float, becomes constant, and also the values of the weight of the solution analyzed, A , and the weight, WS, of the solvent added or evaporated from the solution. If the float is too heavy for the solution and the solvent must be evaporated from the solution, the value of WS takes on the negative sign. According to the calibration results,
G Wl
=
0.30451 ; therefore
G
is equal to 0.2334. The formula for determining the + G concentration of unknown solutions then becomes: ~
Wi
=
100 (0.2334)( A 4- W3) A 0.2334 ( A Wa)
+
-
-4test, of the accuracy of the method as compared with results obtained gravimetrically for the determination of nickel by the glyoxime method showed concordance. The results in terms of grams of anhydrous nickel sulfate per 100 grams solvent were as follows: 30.304 . . . . . . . ......... 30.296
30.250 30.178
Floating equilibrium method.. Gravimetric method . .
969
floating equilibrium method in analyzing solutions for concentration is therefore more accurate than the hydrometer gravity determinations. The values plotted on a curve (Fig. 1) show a comparison with those obtained by gravimetric analysis by Steele and Jackson.6 The values obtained by the float method are slightly higher than these, but this may be due to the difference in values obtained for the components owing to the different methods of analysis used. The float method agrees well with the gravimetric methods made in our own work, the float having been calibrated by the same method as used for the gravimetric data.
30,292 30.284
DISCUSSION OF RESULTS The data obtained on the solubility of the various hydrates of nickel sulfate are given in Table I. All weighings have been reduced to the vacuum basis. Comparison is shown between the float and gravimetric results. The gravimetric analyses are averages of three determinations. TPLBLE I-SC
Temp.
c.
-4.25 -2.00
0.00
3.19 6.00(a)
8
15.65 25. O O b ) 30.001$ b)
..
(C)
31.71 4 0 . 0 0 a) 50.00$$ (b) 53.25 58.21 60.11 79.75 94.22
OF iLUBILITIES CIP HYDRATES
Weight of Solution A 136.8331 146.3774 35.5239 125.2792 145.4360 108.8148 110.4139 112,3565 107.2881 101.7064 109.1731 105.3053 107.6976 107.0614 121.3861 67.0706 102.3786 110 2000 10511427 104.1877 103.4108 96.9927 136.3227
Weight of Solution Added Solvent A Wa 124.9331 118.7795 31.6771 120.2928 145.3731 108.6617 110.2466 126.0980 132.4285 126.0940 142.2885 136.8687 139.7399 142.9922 167.0780 92.8400 150.5640 161 7555 158:0395 159.1173 158 2371 162:9067 245.6684
T X E H Y D R A T € S OF N X U E L S U L F A T E
NICKEL SULFATE
GRAMSNiSO4 + (ANHYDROUS)
+
PI$R
100 G . WATER Float Gravimetric
23.366 26.189 28.884 30.304 30.292 35.491 40.469 40.720 43.719 43.546 43.439 45.299 47.329 47.727 52.267 52 075 54:041 55.389 55 567 64:476 72.597
TYPE OF SALT
23.543 26.087 28.765 30.253 35: i i 4 40.417
FIG.1
i
NiSOa. 7Ha0 (Green)
43:2i39
....
....
45.187 47.437 52:29l
i
NiS04'6Ha0
541009 J 55.177) 55.396 64.217 NiS04'6Ha0 (Green) 72.424)
I n checking with the gravimetric method, the results obtained indicate the applicability of the float method. If it is assumed that the density under standard conditions is a true measure of concentration, then the accuracy of the method depends upon temperature control and the weighings. The weighing of large samples for analysis obviates a painstaking care in the analysis by reducing the effect of small errors in weighing and procedure. Several drops of liquid excess will not influence the final results on such large samples, but the sensitivity of the float does not permit of a variation over one drop, since only one drop makes a decided difference in concentration. Ordinary precautions as to determinations of densities by float hydrometers apply equally well here. The time required for making an analysis is indeed very small when compared with the long gravimetric methods for determining the concentration of constituents present. The ordinary floating hydrometer type with an exposed stem protruding through the surface of the liquid can be used, but the sensitivity is not very great owing to the variation in the surface tension on the exposed stem. One drop of water on a float in equilibrium will cause a sinking, while the effect on an hydrometer float would be negligible. The
The possibilities of the application of the principle of floating equilibrium are very great. Where great accuracy is desired and neither time nor opportunity for making a gravimetric analysis is possible, this method suggests itself. Also, in the analysis for concentrations of solutions such as unstable organic compounds, which require exceedingly great care in analysis because of the unstableness or other difficulties encountered, the float method recommends itself, for when a float is once calibrated for the given solvent and solute, concentrations are easily determined. 0
J . Chem. SOC.(London), 86, 113 (1904).
A Remedy in Sight On several occasions we have called attention to the practice of certain so-called American universities who have offered academic degrees for sale. This campaign has had no success in America, but unfortunately attracted certain individuals in foreign countries much to the embairassment of America. A recent announcement gives reason for hope that the charter given in good faith by a state legislature and officially purchased by the principal offender in marketing degrees may be revoked. The spurious university in question has been cited to show cause why its charter should not be revoked. It is our earnest hope that it may be speedily revoked and this pernicious practice made impossible in future.
Earning Power of Research Recently, a corporation capitalized a t a very substantial figure closed its plants, dismissed its sales force, and practically retired from business. This failure is mainly attributable to the fact that a competitor succeeded in winning and holding certain foreign trade. The successful concern was able to do this because years ago he turned t o research and scientific control, whereas the unsuccessful concern, tardy in its recognition of science, was unfortunate in the selection of its scientificpersonnel, in the choice of its problems, and perhaps did not adequately support a scientific program. It is another instance of the difference between success and failure, success resting with science.
