by the non-volatile glyceride. The viscid residue was further examined and gave a saponification value of 174'1. The amount of crude glycerin yielded was 2.16 per cent. A much larger quantity of the berries was subsequently directly steam distilled and the volatile oil thus obtained was kept in a bottle for about eighteeen months, at the close of which period-baving undergone no perceptible alteration in the meanwhile-it was sent to the Director of the Imperial Institute. In the interval a 10 lb. sample of the whole berries had been sent direct from the Transvaal to the Imperial NOTE ON OILS FROM HEERIA PANICULOSA. Institute in order to ascertain whether the article is likely By C. F. JURITZ. THE following particulars with reference to the presence of volatile and fixed oils in the berry of a certain plant, which grows to the height of twelve feet, is stated to occur abundantly in Zululand and is also found in the Transvaal, may be of some interest. About three years ago M. L. C. von Wissell, of Ndumu, Northern Zululand, sent me 40 lbs. of berries somewhat like currants in outward appearance. They averaged about 7 x 5 mm. in size, were of irregularly ovoid shape, and covered with a shiny hard black, crinkly pericarp, enclosing a soft kernel. This kernel contained a yellowish aromatic fatty substance, solid in some cases and liquid in others. The sender of the sample bad noted that the berry was oleaginous, and wrote that he bad applied the oil to a small festering sore with apparently good results, but that a drop which had accidentally entered his eye had produced slight irritation. The plant producing these berries, said Mr. von Wissell, is known to the Zulus as Isifiku. The root and bark cf the tree, he further stated, contain a coagulable sap somewhat resembling the so-called Japan wax, and, in addition, a dye or tannin. The berries were identified as belonging to Heeria paniculosa (Anacardiaceae), a member of the Rhus or sumach family. Some members of this family are useful, some are acrid, some are poisonous. The mention of the name sumach is sufficient indication of the relevancy of Mr. von Wissell's suggestion regarding the presence of a tannin; in fact, another species of Heeria (Klipboat), which grows in the Somerset West Division of the Cape Province, is actually used for tanning. Moreover, the vegetable fat usually miscalled Japan wax is obtained from the sumach tree (Rhus sp.) cultivated in the far east. | An examination of the berries had previously been made by the Chemist of the Government School of Agriculture, Cedara, Natal, who found them to contain : to acquire any commercial value as a source of oil. The berries were examined in the laboratories of the Institute, the volatile oil yielded by the pericarp being investigated separately from the fixed oil contained in the kernels. These were duly reported on by the Institute, and the results of the investigation, as well as the conclusions drawn therefrom, are abstracted below. The volatile oil from the pericarp amounted to 5'5 per cent of the latter. It was mobile and colourless and free from characteristic odours: the constants were as follows: These results indicate that the oil consists principally of terpenes, and as it has no distinctive odour it would be of little commercial value. The fixed oil derived from the kernels was obtained in the Institute's laboratories by crushing the berries and distilling off the volatile oil. The yield of fixed oil amounted to about 30 per cent from the entire berries. This oil was viscous, clear, and dark brown, and had an aromatic not unpleasant odour. The Director of the Imperial Institute in his report expresses the opinion that the fruits of Heeria paniculosa will not find a ready market in view of the many other superior oil-bearing seeds available. The fruits, moreover, cannot be easily separated into pericarp and seed or kernel, and accordingly there is no commercially feasible way of keeping the fixed oil and the volatile oil separate from each other. If the entire fruits (pericarp and seed together) were used for extraction of the fixed oil, the value of the latter would be diminished by the presence of the volatile oil, and the only way of preventing such a mixture would be to get rid, first of all, of the volatile oil by steam-distilling the entire berries, snd then to obtain the fixed oil from the residue in the still, by submitting it either to pressure or to extraction by solvents, in which case the cost of treatment would be unduly high. Agricultural Chemical Research Laboratory, Department of Agriculture, Capetown, May 10, 1920. MOLECULAR HEAT EQUATION. By FRED. G. EDWARDS. On arrival of Mr. von Wissell's parcel in this laboratory, the berries were air-dried and two separate quantities were then treated by ether-extraction, showing respectively 27.80 per cent and 27.14 per cent of oil of a specific gravity 0820. Nine separate quantities of berries of 200 grms. each were steam-distilled and yielded percentages of volatile oil ranging from 4'47 to 6'07 and averaging 5:00. The volatile oil thus obtained was found to boil at 69° C. under 755'9 mm. pressure. Its specific gravity was 0.823. THE relation between the entropies of different snbstances On heating it changed colour from a light to a dark is shown by G. N. Lewis and G. E. Gibson (Journ. Am. yellow and on further heating decomposed. The above Chem. Soc., Dec., 1917, p. 2554) to be y = f(log T-log 0), results made it evident that a relatively small proportion where e is the temperature at which y is one-half the conof the oil contained in the berries was volatile. The oil stant 5'95; or, in other words, when the molecule conobtained by ether-extraction was subjected to steam distil-tains two atoms in place of one. The degrees of freedom lation, and yielded 17.05 per cent of the volatile oil above in a polyatomic molecule are 3+m, but for a monatomic referred to, corresponding to 4'59 per cent in the air-dry molecule m=0. Such a degree is merely the radial atomic berries. The residual fixed oil remaining after this dis- expansion taking no part in radiation until mo. Between tillation was thick and viscid, and amounted to 89.70 the values of y=2'975 (m2) and y =5'95 (m=0) there is per cent of the total oils extracted by ether, the 6.75 per a point at which m=1, and the position of this point will cent increase being apparently due to absorption of oxygen be at y = 4'462. The general equation is m* = k/log T, Table II. gives absolute temperature for particular values of y = molecular heat, calculated from the formula. The constant k, which is the logarithm of a temperature, is a ratio respectively of the intrinsic pressure, the volume density, or the surface tension, but at present is only relative in the case of water. Dividing k 2-65740 by k=2.8827, the specific density of ice at 273° is obtained at 09218, which reduces to o'908 on recalculating the unit size of molecule. Incidentally this tends to prove that the index x is a function of atomic weight alone, and that Newtonian mechanics are adequate for the interpretation of molecular phenomena, so that the remaining receptacle for quanta is the ether as previously described. Below y=2'975 m=n the number of atoms per molecule, or in the case of compounds the multiples of the unit molecule. The number of electrons is the inverse of n, and physically determines the size of the molecule or ion as the case may be. Where the temperature given by Table II. is above the critical temperature, the pressure is such that the density of a gas is equivalent to that of a liquid. As the temperature of both simple and double salts (the units are presently double) can be calculated at m➡ I with the value of the ratio of k in terms of pressure, the heat of formation can be obtained for different temperature and pressures. The electrons per atom = at m2, and at m = 1, where n =, so that if the metals are at the temperatures The in any given column the contact potentials are zero. potentials are thus measurable with variation of temperature from the points of thermo-electric inversion The Equation of State would contain the terms ka log, where is the number of degrees from the critical temperature, and a is an infinitesimal coefficient to make the ratio of k equal to the critical pressure at the critical temperature. The equations for constant volume can be adjusted to the curves calculated by direct methods to any assigned degree of at constant volume. accuracy. The values of m = I are omitted in the table for the com pounds as they do not correspond with the facts. Doubling the size of the unit molecule, the values respectively for KCl, NaCl, and water, are x = 0.189, 0.18, and o'14288. k = 1983, 2.061, 2.697, and 2.9696 (ice). T 96'31, 115'1, and 498 0. The remaining values for the compounds thus require to be recalculated. The graph of the variation of m between m = 1 and m=0 is a straight line of equation = and if this value be inserted for m above y➡ 2'975 the curves are uniquely determined. The value mo is the point at infinity where the asymptote y = 5'95 meets the curve. At constant volume therefore the number of electrons can never equal the number of atoms. Entropy, expansion, and voltage are determined by the number of electrons per atom or molecule, and the reduction in the size of the molecule by increase of electrons increases the velocity of the molecule in radiation, and therefore the temperature. The use of the molecular-beat equation will lead to im mediate development in all branches of physics, which is rapidly becoming an exact science. The equation gives the tangent at the point y 2'975 to the rectangular hyperbola ny = 5'95. With monatomic gases the electrons must be coincident with the atoms, so that the gas can have no molecular equation. Neutral helium and argon thus contain one electron on alternate atoms. The charged negative and induced positive atoms are independent, so that the atomic heat is constant at the value 2'975. The molecular equation will supersede some standard thermodynamic equations founded upon the assumption that the number of atoms per molecule is a constant. By simplyfying the equations to m=6/y and m=4— (25/3) the error in y is 5 per cent, and can be afterwards adjusted. NEWS polarimetric work. The quartz - mercury vapour-lamp | namely, the direct radiation of the sun, is utilised, the was a great advance in that it provided not only the necessary slit width, while less than that for any other yellow-green line, but several additional lines of lesser in-known source, must still be such as to include a relatively tensity. The best available methods of optical purification large number of wave-lengths. The resultant wave-length are such that a monochromatic source is of little value or so-called optical centre of gravity of such a group of unless the line is sufficiently removed from its immediate | waves can be considered as a monochromatic light source To pump neighbours that nearly complete separation by spectrum | in only a very restricted sense, and finds effective applicafiltration is possible. If sufficient light to satisfy modern practical and research needs is to be obtained from any such source it is necessary to use a relatively wide slit, with a consequent probable inclusion of other wave-lengths in the immediate vicinity of the one desired. When the most intense of all known light sources, tion in but few fields of work. It is especially unsuited to the study of phenomena which change rapidly with change of wave-length. The necessity for obtaining additional intense light sources is consequently imperative. Among the possible sources which have been suggested is that of the rotating arc with cadmium-silver alloy 3000 4000 FIG 2. 5000 6000 electrodes. This source gives a number of fairly intense lines sufficiently isolated from each other and fairly well distributed throughout the spectrum. The writer has carried out many experiments with this source, using an improved rotating arc. It was found impossible to maintain an arc sufficiently free from flicker to give satisfactory results. Another possible source experimented with is the quartz cadmium vapour arc lamp, described by Lowry and Abram (Trans. Faraday Soc., 1914, X., 103). This lamp is always unsatisfactory owing to two defects. It is necessary to have it permanently connected to an air-pump and to immerse the electrodes in water. If the cadmium in a vapour lamp is sufficiently pure, the adhesion between the cadmium and the quartz results in the destruction of the lamp upon the solidification of the cadmium. An improved form of lamp has been brought out by Sand (Proc. Phys. Soc., 1915-16, xxviii., 94). In this type the tendency of the cadmium to adhere to the quartz walls is stated to be lessened by introducing into the lamp a small amount of zirconia in the form of fine powder. The cadmium is placed in a side tube connected to the pump, and the body of the lamp by a tube constricted to three capillaries for the purpose of filtering the metal. Additional filtering day be obtained by introducing a roll of iron gauze. Extensive experiments by the writer with this type of lamp have demonstrated that it is impracticable, provided a pure cadmium spectrum is desired. The method of filtering suggested is inadequate. The impurities introduced into the lamp by this method of filling undoubtedly have a | tendency to prevent breakage, but effectively prevent obtaining a relatively pure intense cadmium spectrum. In order to eliminate all oxide and other impurities from the cadmium used in filling, it is necessary to carefully distil the cadmium into the body of the lamp. Upon allowing the lamp to cool, adhesion between the quartz and the metal takes place in spite of the presence of the zirconia. If the lamp does not crack upon the first solidification of the cadmium thin sections of the quartz are peeled from | the walls by the contracting metal. Upon cooling a second time the lamp was invariably cracked. Numerous experiments of varied character failed to overcome the constant breakage of the Sand lamp. Among the filling mixtures tried was a cadmium-mercury alloy. The percentages of the constituents were varied on a wide range. The introduction of the mercury is very effective in preventing the cracking of the lamp, as the alloy formed was so soft that no appreciable adbesion between it and the quartz resulted. It was found, however, impossible to obtain a brilliant cadmium spectrum under any circum stances. The vapour-pressure of the mercury being so much higher than that of the cadmium, resulted in the electric energy being almost entirely carried by the mercury, and the usual brilliant mercury spectrum resulted. In view of the preceding facts it is evident that a serviceable brilliant cadmium - vapour lamp might be obtained by alloying the cadmium with a suitable element of lower vapour-pressure. Through the ccurtesy of Dr. W. F. Hillebrand, a quantity of the little known element, gallium, was obtained. The material was in a very impure condition, containing approximalely 10 per cent indium. The freezing-point was below 22° C., at which temperature it was a liquid with a viscosity less than that of mercury. A study of the impure material was made by Dr. G. E. F. Lundell, who succeeded in obtaining the gallium in a relatively pure condition. Crude gallium was dissolved in aqua regia, treated with sulphuric acid, and fumed to remove nitric acid. After dilution small amounts of lead sulphate were filtered off. The solution was then diluted, treated with hydrogen sulphide, and filtered to remove the hydrogen sulphide group of elements. The filtrate was boiled to expel hydrogen sulphide and treated with ammonium hydroxide. The precipitate was filtered off, dissolved, and reprecipitated three times to free it from zinc. The final separation from indium was based on the solubility of gallium hydroxide in a solution of sodium hydroxide, and the insolubility of indium hydroxide in that reagent. The sodium hydroxide separation was carried through three times. The deposition of gallium was finally carried out by electrolysis of the alkaline solution as recommended by Ubler and Browning (Am. Journ. Sci., Fourth Series, 1916, xlii., 389). The purified gallium had a freezing-point of approxi mately 30° C. This surprising fact has since been verified by the careful work of Richards, who has definitely fixed this temperature at 30·8° C. (Fourn. Am. Chem. Soc., xli., 131). Regarding the boiling point of this element bat little is known. The few experiments which have been made are in agreement that it is above 1500° C. This property should make it an ideal substance for the purpose in hand, provided it would alloy with cadmium. The first experiment demonstrated that it united with cadmium with the utmost ease. In fact, the addition of a few drops to 10 or 15 cc. of cadmium completely changed the texture of the latter, rendering it relatively soft and greatly reducing its tensile strength. Subsequently it was discovered that upon distilling the cadmium from the alloy at a pressure of 0.001 mm. of mercury, the minute quantity of gallium carried through was sufficient to completely change the character of the cadmium and to prevent adhesion between the cadmium and the walls of the lamp. The type of quartz lamp used in the experiments is that shown in Fig. 1. The total volume is approximately 10 cc. The electrodes consist of tungsten wires (B) entering through quartz capillaries. They are closed with lead seals similar to the type described by Sand (Proc. Phys. Soc., 1914: xxvi., 127). In filling the lamp the cadmium containing 2 or 3 per cent gallium is placed in the bulb F. It is necessary to maintain the pressure in the lamp and connections below o'001 mm. of mercury with the exception of that due to the cadmium and gallium, throughout the process of distilling. Owing to the fact that the volume of the lamp is relatively small, the quartz capillary at E should be of such a length as to permit of sealing off in the shortest possible time. The flame used for this purpose should be small, and the heating of the tube on both sides of the capillary should be prevented as far as possible. The method indicated above, if carefully followed, will give a lamp with indefinite life. One of this type has been in intermittent use for over a year and shows no sign of deterioration. Should traces of oxide or stains due thereto appear during the process of filling, they can readily be reduced by introducing pure dry bydrogen and heating. The lamp may be started by heating with a flame to vaporise the metal. It is in all cases advisable to have a current of air blowing upon the lead seals to keep them cool. If the blast is allowed to strike the body of the lamp the cadmium is condensed and obscures the arc. The most convenient source of energy for operation is the ordinary 110 volt lighting circuit, on which it will operate continuously with a current as small as 3 amp., and drop of 14 volts across the terminals of the lamp. The most satisfactory results, however, are secured with a current of about 7 amp. and a drop across the terminals of about 25 volts. Under this condition a practically pure cadmium spectrum of great brilliancy is obtained. The intensity secured is apparently equal to that which would be obtained were the lamp filled with cadmium alone. The map of the spectrum of gallium given in Fig. 2 is interesting (Eder and Valenta," Atlas Typischen Spektren "). The wavelengths and intensities of the lines are given in Table I. in this connection. It will be observed that there are but five lines in the visible spectrum and that from practically 4200 A to 6400 A there are no lines. When the lamp is operated at a temperature sufficiently high to bring the quartz to a cherry-red colour, and there is danger of softening the lamp, several gallium lines become faintly visible. The investigations of Uhler and Browning indicate the possibility of two gallium lines 5353.81 A and 5359·8 A (Am. Journ. Sci., 1916, xlii., 389). However, these lines, if present, are so faint at the highest temperature at which the lamp can be operated that they cannot be identified. The cadmium spectrum is thus obtained in a condition exceedingly favourable for those purposes for which an intense monochromatic light source is indispensable. No gallium lines are found between 4200 A and 6400 A, and the gallium lines which are detectable have so low an intensity that they are wholly negligible in polarimetric and other fields of work. "Now, in all methods of finding drop size by allowing liquid to enter the drop, however slowly, until it breaks away, the hydrostatic pressure of the liquid at any level within the drop is unknown, but the following relations hold. If P is any point on the surface of the drop (which is a figure of revolution) and P a b a normal to the surface, then if the hydrostatic pressure in the oil at the level P exceeds that in the water at the same level by the amount dynes per sq. cm., t the surface tension in dynes per cm. and are related thus: 6396.99 8 6 There are now available practically no dependable intense monochromatic red light sources. Any souice to meet modern demands must permit of continuous operation with minimum amount of attention and an absence of flicker. The very pure red line (λ = 6439 A) of cadmium seems to be the only possible source of sufficient intensity in this region of the spectrum. It is believed that the cadmium-gallium lamp will make this much needed source, as well as other lines of the cadmium spectrum, available for many lines of endeavour. The writer desires to acknowledge his indebtedness to Mr. F. P. Phelps for valuable assistance in the experimental work.-Philosophical Magazine, xxxix., No. 231. THE THEORY AND PRACTICE OF LUBRICATION: at the point P. At a lower point P1 the same is true, but here the difference of pressure is less by the amount (density of water-density of oil) x PM xg. All distances in cm. and g in this latitude 981. As the drop grows there comes a time when the differences of hydrostatic pressure By HENRY M. WELLS and JAMES E. SOUTHCOMBE, M.Sc. and the lengths Pa Pb in different parts of the drop are (Concluded from p. 272). DISCUSSION (continued). PROF. C. V. Boys, in a letter to the Scientific and Industrial Research Department, writes as follows: becoming incompatible, and instability results. The breaking depends on differences of hydrostatic pressure within the drop as compared with the surrounding water which determine the rupture. The actual hydrostatic pressure is not known, and its determination by elimination "I notice that the conclusions arrived at by Messrs. along the measurements of Pa Pb at a number of points, Wells and Southcombe depend on the determination of oil-water surface tension, or rather of comparative values, by the method of counting of drops. As a general proposition I very much doubt the conclusion that the number of drops in a given volume is inversely as the surface tension, although it may be for some particular pair of liquids or with a particular difference of density. The mere fact that the difference of density of the two liquids, which is one of the operative factors in determining the drop size, is not included in the statement and appears to be ignored is alone sufficient to raise very serious doubts; but quite apart from this the very complicated conditions which determine the moment of instability or the breaking off of a drop themselves appear to me to be incompatible with any such convenient conclusion. I say convenient conclusion because if the method were correct in principle it could not be surpassed in ease of application. "My object is not destructive criticism, but a desire to propose an absolute method of determining the actual surface tension of the water-oil surface in CGS or other definite units. It seems to me of the first importance, as the conclusions of the authors are based on comparative measures of surface tensions, that the method of making the measures should be above suspicion; further, mere comparative measures, even if correctly comparable, are less desirable than absolute measures. * From the Journal of the Society of Chemical Industry, March 15, 1920. WATER w OIL In a paper P would be very tedious and inaccurate. |