July 15, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
297
for several varieties of nuts. From this table it is evident that the spaces in the cream-test bottle occupied by 1gram of oil vary slightly with each variety. The average of all the tests was 11.18 spaces occupied by 1 gram of oil. Using the factor 11.18 gives results very near to those obtained by the gravimetric method, as seen in Table 11. Greater accuracy, however, can be obtained by using the individual factor for each variety of nuts, but this does not seem necessary for most work. More work needs to be done a t this point and will be undertaken when time permits.
The percentages of oil as determined by the petroleum ether extraction and the new method are shown in Table 11. Samples of each variety were collected from two different localities and the determinations made in duplicate. The results are found to compare favorably. Table I11 shows a comparison of the physical and chemical characteristics of pecan oil extracted by expression and by the two foregoing methods. This table shows the oil from the different methods to have practically the same properties. The refractive index and specific gravity were the same with all three methods. The iodine number and saponification number were highest with the new method, indicating that a TABLE111. CHEMICAL AND PHYSICAL CHARACTERISTICS OF PECANOIL EXTRACTED BY EXPREBSIOM, PETROLEUM ETHER, purer oil was obtained by this method. AND NEW METHOD ACKNOWLEDGMENT (Stuart variety) REFRACTIVE The author wishes to express his indebtedness to A. 0. IODINE INDEX SPECIFIC Alben, Pecan Soil Fertility Laboratory, U. S. Bureau of No. (ABBB RE- SAPONI- GRAVITY M ~ T H OOF D (WIJS FRACTOME- FICATION (WESTPHAL Chemistry and Soils, Shreveport, La., for valuable suggesEXTRACTINQ METHOD) TBR) No. BALANCE) COLOR tions and kind assistance in connection with this work. Light golden 1.4670 189.89 Expressed 102.86 0.9190 Petroleum ether 103.27 New method 103.83
1.4670 1.4670
187.80 189.95
0.9190 0.9190
Light golden Colorless
RECEIVED December 23, 1931.
Graphic Calculations in Water Analyses JOHNKENNETHSELLERS, Copper Queen Laboratory, Bisbee, Ariz.
T
HE facts that the existing methods for calculating the
elements and radicals present in mineral waters into certain hypothetical combinations are many and diverse, rendering the results of such calculations confusing and not readily comparable one with the other, and that modern ahemical knowledge Eully justifies no such calculations, are diverting the general tendency toward the ionic form of stating the results of water analysis. The practice of combining the ions, however, still finds extensive application in industry] and various schemes have been evolved whereby these calculations are reduced to a routine applicable by the operator with limited chemical training. The use of milligram equivalents (or reacting values) in water analyses has long been practiced (1,4), and anelaboration on the use of equivalents has been made by graphically r e p r e s e n t i n g the results of analysis (2’8). These graphic representations have been employed for a number of years in p u b l i c a t i o n s of the U. S. Geological Survey. The use of equivalents may be further extended to thelength of integrating the hypothetical combinations by mechanical methods. I n the method herein advocated, a determination of calcium, magnesium] carbonate, sulfate, and chlorine is made. The results, stated as parts per million, are converted to the milligram equivalents per kilogram (Stabler’s reacting values, 4) by multiplying by the rec i p r o c a l s of the c o m b i n i n g weights of the respective ions. The r e s u l t s being thus conFIGURE1
verted, any ion may be combined with any other ion in numerically equal quantities. The advisability of determining the sodium and potassium is contingent upon the accuracy desired, and when sodium and potassium are not determined, such an amount of sodium is “written in” as will cause the sum of the equivalents of the acid radicals to be exactly equal to the sum for the bases. The probability of the two sums balancing when all of the ions are determined is very small, and the small difference usually existing is distributed so as to effect a balance.
FIGURE 2 The equivalents of the positive and negative radicals, being thus adjusted, are then consecutively laid out on prepared coordinate paper (calibrated in milligram equivalents) on either side of a central line (Figure 1). The length on the graph representing an ion may be called the “reacting length” of that ion. Since linear distance on the graph is quantitatively proportional to the equivalents of the ions, it is also proportional to the equivalents of the compounds. All radicals lying laterally contiguous are combined, and the compounds supposedly present in the sample may thus be instantly visualized. The failure of two radicals to lie laterally adjacent connotes the absence of the compound composed of those two radicals. The results as read from this graph are in terms of milligram equivalents and necessitate a conversion into the desired units. A series of graphic scales, one for each possible compound, are constructed for this purpose (Figure 2) and may be used indefinitely,
298
ANALYTICAL EDITION
To convert the calcium carbonate, distance ab (Figure l), the reacting length of the calcium carbonate, is transferred t o scale a (Figure 2) by means of a pair of dividers, and the result is read directly in terms of parts per million of calcium carbonate. The length representative of 1 part per million of calcium carbonate (scale a) may be called the “factor length,”and bears a ratio to the length representing 1 milligram equivalent on the graph, equal to the reciprocal of the factor for converting the milligram equivalent of calcium carbonate into p. p. m. of that compound. The factor length is determined by dividing the reacting length unit by this combination factor. Foulk (4) presents a discussion and a list of these combination factors. All other scales are made and the conversions executed in accordance with the foregoing procedure. The scales may be adjusted to give results in any unit desired, such as grains per gallon, pounds per 1000 gallons, etc. When the linear counterpart of 1 milligram equivalent is a suitable length, for example 2 or 3 cm., the method may be applied without resort to graph paper. The numerical react-
Vol. 4, No. 3
ing values of the ions may be converted into the reacting lengths by the use of a vernier slide micrometer. These lengths are plotted on either side of a straight line drawn on a clean sheet of paper, and the conversion t o the desired units made with dividers and the scales as usual. The method is, of course, independent of the system or order of combining the radicals, the order employed above being arbitrarily selected for the purpose of demonstrating the method. The accuracy of this method varies directly with the length taken as unity in the graph. LITERATURE CITED (1) Assoc. Official Agr. Chem., “Official and Tentative Methods of Analysis,” p. 104 (1925). (2) Collins, W. D., IND.EXQ.CHEY., 15, 394 (1923). (3) Collins, W. D., U. S. Geol. Survey, Water Supply Paper 596-H, 253-61 (1928). (4) Foulk, C. W., Geol. Survey Ohio, Industrial Water Supplies, Bull. 29, 16-27 (1925).
RECEIVED November 14, 1931.
Pressure Pump for Circulating Gases in a Closed System E. B. KESTER,U. S. Bureau of Mines, 4800 Forbes St., Pittsburgh, Pa,
I
N AN investigation of the action of oxygen on lowtemperature tar when recirculated through the material in a closed system, it was necessary to devise a pressure pump able to overcome the strong resistance created by the viscous column of tar through which the gas was to be forced. To this end, a non-mechanical pump operated by an external water-pump through a mercury medium was construct>ed which would circulate Glass wool 6 to 20 liters of gas B per hour and which i“ Glass beads would o p e r a t e day and night without att e n t i o n . It has an advantage over other p u m p s described in the literature in its simplicity of design, or in its lack of solid m o v i n g p a r t s and bearing surfaces. The underlying principle is somewhat similar to that of the pump d e s c r i b e d by M a a s s ( I ) , b u t the construction is more compact and t h e operation less complicated. The water-pump is connected to e, as in Figure 1. The suction produced reduces the pressure in f, a, and b which causes the mercury to rise in a and b and to go down in c and d.
When the level of the mercury in c reaches point i in b, a difference of pressure between atmospheric and that obtaining in voids of f,a, and b greater than the height of the mercury slug in b, is quickly established. The result is that the slug is shot forcibly into f, thus relieving the vacuum in e, f,and a. The mercury level in a therefore drops suddenly, forcing the level in d upward. At the same time the air intake is cut off by c’s filling with mercury as before, and the cycle repeats itself. The pulsating motion of the mercury level in d, together with the valve arrangement g and h, makes circulation of the gas through the closed system possible. Tube e is filled with glass beads and glass wool to trap stray globules of mercury. The capacity of the stroke in d is affected by changes in diameter of a; for a larger diameter of the latter more mercury is raised per unit height and consequently more drawn from d. Tube b is necessarily small if the slug of mercury is to be kept from breaking and hindering air admission through c. The return to atmospheric or nearly atmospheric pressure of voids in a and c can be expedited by multiplying b by two or more. For the same reason, the connection of e with the water-pump should be short and should not contain a safety-trap in series. None, in fact, is required in this apparatus. The presence of an unnecessary amount of space to be evacuated and returned to the higher pressure merely lowers the effectiveness of the pump-that is, the larger this space the more there is to be filled with air in the short time elapsing between the shooting of the slug and the cut-off of air-intake through c. Likewise the space between the valves and pump-that is, the space above the mercury level in d at top of stroke and connecting line-should be small, so that only a very little of the stroke is wasted in compression before the valve operates. LITERATURE CITED (1) Maass, O., J. Am. Chem. SOC.,41, 53-9 (1919). RECEIYBD January 29, 1932. Published by permission of the Direotor, U. S. Bureau of Mines. (Not subject to copyright.)
