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CHEMICAL NEWS,

The acid has the composition and chemical properties of an a brom-88-phenylchlorpropionic acid; it gives benzoic acid on oxidation with potassium permanganate, a-bromcinnamic acid and potassium chloride when boiled in alcoholic solution with potassium acetate, and a-brom-3phenyllactic acid when digested with hot water. The acid is different, however, from the known substance of this composition and structure; it melted 10° lower, and a mixture of the two began to melt 20° to 25° below the lower melting component. The ether-ligroin from which all acids had been removed by extraction with sodium carbonate left after evaporation a small quantity of nonacid substances that were not identified.

These results show that aluminium chloride removes both hydrobromic acid and bromine from phenyldibrompriopionyl chloride, and that action takes place slowly even at the temperature of a freezing mixture. The effect must be due to the phenyl group in the 8-position, because dibrompropionyl chloride forms a double compound with aluminium chloride which is perfectly stable at the ordinary temperature. Phenyldibrompropionyl Chloride and Benzene.-After trying various methods of procedure, we adopted the following:-Sixty grms. of ground aluminium chloride were added to a solution 121 grms. of the acid chloride and 50 grms. of benzene in 250 cc. of carbon bisulphide. The mixture was kept at 20 for twenty-four hours, and then poured into iced hydrochloric acid. The carbon bisulphide layer on evaporation deposited a solid that was purified by re-crystallisation from absolute alcohol. It gave 63 grms. of a substance that separated in very pale yellow needles melting at 89-90°. This is evidently the product that had previously been obtained from the same reaction by Collet. Our analysis shows, however, that it is not phenyldibrompropiophenone :

o 1879 grm. substance gave o‘4295 grm. CO2 and 0.0646 grm. H2O.

2-Brom-3-keto-1-phenyl-2.3-dihydrindene reacts readily with organic and inorganic bases, and also with potassium acetate, but it is difficult to isolate pure substances from the products. The substance is most easily identified by means of the semi-carbazone obtained by adding an aqueous solution of semi-carbazide hydrochloride and potassium acetate to an alcoholic solution of the ketone :

The unsaturated semi carbazone separates in minute yellow needles which, after re-crystallisation from alcohol and acetone, melt with decomposition at 212°. The same substance is formed when the yellow oil, obtained by boiling the halogen compound with alcoholic potassium hydroxide, is treated with semi-carbazide.

Phenyldibrompropionyl Chloride and Brombenzene.—The reaction takes place much more slowly than the corre sponding reaction with benzene, and consequently leads to the formation of a larger quantity of acid by-products due to the interaction of the acid chloride and aluminium chloride. These acid products were removed by extraction with sodium carbonate. The extracted solution, on dilu tion with ligroin, deposited a solid which, after repeated crystallisation from chloroform and absolute alcohol, melted at 143-144°. The substance crystallises in colourless needles, sparingly soluble in ether and alcohol, readily in acetone.

Analysis.

0 1518 grm. substance gave o‘2762 grm. CO2 and 0.0358 grm. H2O.

The bromine compound reduces potassium permanganate dissolved in acetone-slowly at the ordinary temperature, rapidly near the boiling-point of acetone. The sole organic oxidation product is p-brom-o-benzoylbenzoic acid. This was purified by crystallisation from methyl alcohol. It separated in large flat needles or plates melting at 174°.

Analysis.

01540 grm. substance gave o‘3109 grm. CO2 and 0.0436 grm. H2O.

These results prove that the principal product of the reaction between phenyldibrompropionyl chloride and brombenzene is 2.6-dibrom-3-keto-1-phenyl-2.3-dihydroindene,

an indene derivative with bromine in each nucleus :C6H5CHBICH BrCOC1+ BrC6H5

CHC6H5 CHBr

Br

=

CO

+HCI+ HBr.

Analysis.

01834 grm. substance gave o‘3334 grm. CO2 and 0.0409 grm. H2O.

Only substances related in this way could be formed in the reaction with brombenzene, and also give p-brom-obenzoylbenzoic acid on oxidation. Formula II. is, however, exceedingly improbable for either of the substances in question, because, judging from the observations made with the corresponding triphenylindene derivative (III.), the bromine in a compound with this structure would be as reactive as the bromine in triphenylbrommethane. This is not the case. It is much more probable, therefore, that the substances are stereoisomers (I.). This conclusion is supported by the ease with which the higher melting is transformed into the lower melting substance by heating. A perfectly clean and almost complete transformation is obtained by keeping it at its melting-point for an hour.

PAINTS.

Strength Test.

is

THE strength of pigments does not bear a very close relationship to the chemical composition, hence a quantitative analysis does not necessarily give the information actually desired. For this reason the "strength test of great importance. A standard colour is usually selected, but in case no standard is used all of a series of similar colours may be compared with one another.

Weigh equal portions of the samples to be tested, and, if available, a standard sample; add to each equal portions of pure zinc oxide, the amount depending upon the character of the colour tested (this may vary from 5 to 60 times that of the colour). Rub up each mixture on a glass plate or, better, a stone slab, until there is no change in shade on further rubbing. Rate the samples in the order Buletin No. 109, Revised, U.S. Department of Agriculture Bureau of Chemistry.

*

similar way by grinding up each with the same coloured pigment, such as Venetian red. With yellows use chrome green or Prussian blue instead of a white diluent. Add the same number of drops of raw linseed oil to all samples in grinding for the strength test.

White Pigments.

1. White Lead.-Pure white lead is basic carbonate of lead and should approach the following composition: 2PbCO3Pb(OH)2. It should be completely soluble in acetic acid. Test for barium and calcium by the flame test. Use an iron wire, as platinum will be ruined by the lead.

(a) Total Lead.-Weigh I grm. of the sample, moisten with water, dissolve in acetic acid, filter, and wash, ignite, and weigh the insoluble impurities. To the filtrate from the insoluble matter add 25 cc. of sulphuric acid (1 : 1), evaporate and heat until the acetic acid is driven off; cool, dilute to 200 cc. with water, allow to stand for two hours, filter on a Gooch crucible, wash with I per cent sulphuric acid, ignite, and weigh as lead sulphate. Calculate to total lead (PbSO4 x 0.68292 = Pb), or calculate to basic carbonate of lead (white lead) by multiplying the weight of lead sulphate by o·85258.

The filtrate from the lead sulphate may be used to test for other metals, though white lead is only rarely adulterated with soluble substances; test, however, for zinc, which may be present as zinc oxide.

Instead of determining the total lead as sulphate it may be determined as lead chromate by precipitating the hot acetic acid solution with potassium dichromate, filtering on a Gooch crucible, igniting at a low temperature, and weighing as lead chromate.

(b) Complete Analysis.-When it is necessary to determine the exact composition of a pure white lead, heat I grm. of the pigment in a porcelain boat in a current of dry carbon-dioxide-free air, catching the water in sulphuric acid and calcium chloride and the carbon dioxide in soda lime or potassium hydroxide (1.27 specific gravity). By weighing the residue of lead monoxide in the boat all the factors for determining the total composition are obtained. Figure the carbon dioxide to lead carbonate (PbCO3), calculate the lead monoxide corresponding to the lead carbonate (PbCO3) and subtract from the total lead monoxide, calculate the remaining lead monoxide to lead hydroxide (Pb(OH)2), calculate the water sponding to lead hydroxide and subtract from the total water, the remainder being figured as moisture.

corre

This method assumes the absence of acetic acid. Thompson (Journ. Soc. Chem. Ind., 1905, xxiv., 487) states that acetic acid varies from 0.05 per cent in Dutch process white lead to o'7 per cent in some precipitated white leads. It is then more accurate to determine the carbon dioxide by evolution; this is especially the case when working with a lead extracted from an oil paste, as the lead soap and unextracted oil will cause a considerable error by the ignition method. In determining carbon dioxide by the evolution method, liberate the carbon dioxide with dilute nitric acid, have a reflux condenser next to the evolution flask, and dry the carbon dioxide with calcium chloride before absorbing it in the potassium hydroxide bulbs.

(c) Acetic Acid.-It is sometimes necessary to determine acetic acid. The Navy Department specifications demand that white lead shall not contain "acetate in excess of fifteen one-hundredths of 1 per cent of glacial acetic acid." Thompson's method (Fourn. Soc. Chem. Ind., 1905, xxiv., 487) is as follows:

Eighteen grms. of the dry white lead are placed in a 500 cc. flask, this flask being arranged for connection with a steam supply, and also with an ordinary Liebig condenser. To this white lead is added 40 cc. of syrupy phosphoric acid, 18 grms. of zinc dust, and about 50 cc. The flask containing the material is heated of water. directly and distilled down to a small bulk.

Then the

steam is passed into the flask until it becomes about half full of condensed water, when the steam is shut off and the original flask heated directly and distilled down to the same small bulk-this operation being conducted twice. The distillate is then transferred to a special flask and I cc. of syrup phosphoric acid added to ensure a slightly acid condition. The flask is then heated and distilled down to a small bulk-say, 20 cc. Steam is then passed through the flask until it contains about 200 cc. of condensed water, when the steam is shut off and the flask heated directly. These operations of direct distillation and steam distillation are conducted until 10 cc. of the distillate require but a drop of tenth-normal alkali to produce a change in the presence of phenolphthalein. Then the bulk of the distillate is titrated with tenth-normal sodium hydroxide, and the acetic acid calculated. It will be found very convenient in this titration, which amounts in some cases to 600-700 cc., to titrate the distillate when it reaches 200 cc., and so continue titrating every 200 cc. as it

distils over.

If the white lead contains appreciable amounts of chlorine it is well to add some silver phosphate to the second distillation flask and not carry the distillation from this flask too far at any time.

The method used by the chemists of the Navy Department is as follows:-Weigh 25 grms. of white lead in an Erlenmeyer flask, add 75 cc. of 25 per cent phosphoric acid, distil with steam to a 500 cc. distillate, add to the distillate some milk of barium carbonate, bring to a boil, filter, keeping the solution at the boiling point (it is not necessary to wash), add an excess of sulphuric acid to the filtrate and determine the barium sulphate in the usual manner; subtract 53 mgrms. from the weight of the barium sulphate and calculate the remainder as acetic acid (BaSO4 × 0.515= CH3COOH). The object of this rather indirect method is to avoid any error that might arise from fatty acids being carried over by the steam distillation. For white lead that has not been ground in oil, Thompson's method is to be preferred.

2. Lead Zinc Whites.-French zinc is practically pure zinc oxide, being made from metallic zinc. American zinc is made by roasting zinc ores, and almost always contains some lead. Sublimed lead is made by volatilising galena, and as sphalerite is usually associated with the galena, it nearly always contains zinc oxide in addition to the basic sulphate of lead. Zinc lead is essentially lead sulphate and zinc oxide.

(a) Moisture.-Dry 2 grms. for two hours at a temperature of 105° C.

(b) Soluble Sulphate.-Boil 1 grm. of the sample with 75 cc. of water and 25 cc. of alcohol, filter, wash with a mixture of alcohol and water (1 : 3), and determine sulphuric acid in the filtrate by the usual method of precipitation with barium chloride. The soluble sulphate may be calculated to zinc sulphate.

(To be continued).

Isomerisation of Oleic Acid by Displacement of the Double Bond.-A. Arnaud and S. Posternak. Saytzeff thought that by treating iodostearic acid with alcoholic potash he had obtained an isomer of oleic acid, which he called isoleic acid, in which the double bond was displaced one carbon to the right towards the carboxyl. The authors have, however, found that the reaction is much more complicated, four acids being formed, viz. :-Ordinary elaidic acid, 49.10; elaidic acid, 48.9; oxystearic acid, C18H3603; and the original oleic acid, 19.10. The fixation of a molecule of hydriodic acid by oleic acid and the sub. sequent removal of it by alcoholic potash induces at least three different reactions:-(1) Transformation of the oleic acid into its stereochemical isomer; (2) displacement of the double bond towards the hydroxyl; (3) replacement of the iodine in the iodostearic acid by a hydroxyl.—Comptes Rendus, cl., No. 23.

PROCEEDINGS OF SOCIETIES.

PHYSICAL SOCIETY.

Ordinary Meeting, July 8th, 1910.

Prof. H. L. CALLENDAR, F.R.S., President, in the Chair. A PAPER entitled "The Radio-balance; a Thermoelectric Balance for the Absolute Measurement of Radiation; with applications to Radium and its Emanation," was read by the PRESIDent.

In this apparatus, which was first constructed in 1905, and was briefly described in an article on Radiation contributed to the "Encyclopædia Britannica," heat supplied by radiation is directly compensated by the Peltier absorption of heat in a thermo-junction through which a measured electric current is passed. In the simplest form of the instrument, radiation admitted through a measured aperture, 2 mm. diameter, falls on a small copper disc 3 mm. diameter, by 5 mm. thick, to which two thermo-junctions are attached, forming a Peltier cross. One couple is connected to a sensitive galvanometer for indicating changes of temperature. The other is connected to a battery and theostat in series with a millammeter or potentiometer for measuring the current required to reduce the deflection of in sq. cm., Q the intensity of the radiation in watts per sq. the galvanameter to zero. If A is the area of the aperture cm., a the absorption-coefficient of the surface of the disc, P the Peltier coefficient in volts, C the balancing current in ampères, and R the effective resistance of the couple, the equation giving the value of the radiation in absolute measure is

aAQ PC-CR.

The absolute value of P is the product of the absolute temperature by the thermoelectric power. The value of R, in the small correction term for the Joule effect, is readily determined by observing the neutral current, C1 = P/R, for which the Joule effect balances the Peltier effect. In practice two similar discs with similar connections are mounted side by side in a thick copper box, and are balanced against each other in order to avoid changes of zero due to exposure to sunshine, or rapid variations of temperature.

The advantages of the disc radio-balance are that it is very simple to construct and easy to reproduce without material variation in the reduction constants. It is very suitable for measurements of solar radiation, or strong sources, but is insufficiently sensitive for weak sources; and the absorption coefficient a must be determined by comparison with a standard.

In the cup radio-balance, the radiation is received in a copper cup, 3 mm. diameter by 10 mm. deep, so that the absorption coefficient is practically equal to unity. Greater sensitiveness is secured by employing a pile of several couples, insulated from the cup, in place of the single balancing couple. External disturbances are eliminated by employing a pair of cups, similarly mounted but oppositely connected, enclosed in a thick copper cylinder. The Joule effect, represented by the CR term in the equation, is automatically eliminated by passing the same current in series through the opposing Peltier junctions soldered to the bottom of the cups. The cup exposed to radiation is cooled, and the cup screened from radiation is heated by the Peltier effect, while both are equally heated by the Joule effect. A complete observation involves reversing the current and switching over the radiation screen, in order to eliminate any difference of sensitiveness of the two piles. By observing the neutral current, each cup can be used separately, as with the disc balance, but the disc balance cannot be used with the Peltier couples connected in opposition, unless the balancing couples are insulated from the discs. The cup radio-balance is sensitive to less than a tenth of a microwatt, and is very suitable for

NEWS

A paper on Hysteresis Loops and Lissajous' Figures, and on the Energy wasted in a Hysteresis Loop was read by Prof. S. P. THOMPSON.

The instruments exhibited at the meeting included (1) a disc radio-balance equatorially mounted for solar radiation; (2) a laboratory pattern, with water or steam jackets for determining the temperature coefficients, and for investigating the theory of the instrument; (3) a cup radiobalance, with which the heat production of radium and its emanation were demonstrated. The latter instrument is capable of measuring the heat evolved from 1 mgrm. of radium to about 1 part in 1000.

Dr. J. A. HARKER expressed his interest in the paper, especially in the details of the construction of the various instruments exhibited.

Mr. A. CAMPBELL asked what were the materials of the wires used for the thermo-couples.

The PRESIDENT, in reply to Mr. Campbell, said he had used iron-constantin couples.

A paper entitled "The Convection of Heat from a Body cooled by a Stream of Fluid" was read by Dr. A. RUSSELL. Attention is directed to certain deductions made by Boussinesq from the mathematical theory of the conduction of heat in liquids. Complete proofs are given of Boussinesq's formulæ, stress being laid on their limitations, and some of their practical applications are pointed out. It is proved that when a hot body is immersed in a stream of liquid flowing with constant velocity, the cooling is proportional to the difference of temperature between the body and the liquid. Newton proved experimentally in 1701 that this law was true for the case of a hot body being cooled by a draught of air. He enunciated his law with reference to the forced convection of heat from a body, and not, as is often stated, to the natural free convection from it. Lorenz has shown that in special cases the natural convection of heat will vary as the 125th power of the dif ference of temperature. Provided that the velocity of the cooling draught is kept constant between certain limits, Compan has shown that Newton's law is very approximately true even when the difference of temperature is as high as 300° C. Another deduction from the formulæ proved in the paper is that the cooling is very approximately proportional to the square root of the velocity of the

convection current.

The author gives the solution of the problem of the heating of a liquid flowing steadily, with a velocity less than the critical velocity, through a cylindrical tube which is maintained at constant temperature. It is shown that, in many practical cases, the heating power of the tube varies as ResokVl, where R is the radius of the tube, e the difference of temperature between the tube and the liquid, s the specific heat, o the density, k the conductivity, V the velocity of flow, and the length of the tube.

It is proved that if a wire be immersed in a stream of liquid with its length at right angles to the direction of flow, the electric current which will fuse the wire varies as the 125th power of the diameter of the wire.

Finally, the effect on the cooling of an electrically heated cylinder by a stream of liquid, of putting an insulating wrapping round it, is considered. It is shown that in certain cases the effect of this procedure is to lower the temperature of the cylinder, an effect which can be easily demonstrated experimentally. In order to simplify the mathematical work, only the case of incompressible fluids is considered. Experimental results, however, obtained by various physicists are quoted to show that some of the

Attempts have been made to find an explanation of the exhibited by iron and steel when subjected to cycles of forms of the looped curves which express the hysteresis magnetisation. Physical explanations to account for their general shape have been given by Ewing and Hopkinson, and M. Pierre Weiss has put forward an electronic theory to account for the principal features. The author shows that any hysteresis loop can be analysed into a harmonic series of closed curves corresponding to the various terms in the analysis of the current wave, and their constituents are examined in the paper. A number of examples of hysteresis loops were chosen and subjected to analysis. steel, hard and soft, solid and laminated, and taken by The loops chosen related to various kinds of iron and various methods. In carrying out the analysis the simple approximate method described by the author (Proc. Phys. Soc., vol. xiv.) was used. Details are given of the analysis of various loops, the effect of eddy currents on the size and form of the loops is discussed, and an account is given of the effect of the higher sine and cosine constituents of the current wave.

Dr. RUSSELL thanked the author for his most interesting and instructive paper. In connection with Dr. Thompson's orthogonal ellipse, he showed how an indefinite number of two-beaked loops similar to the hysteresis loop can be made up by quadrants of ellipses, each loop having the same height, the same area, and the same breadth as the orthogonal ellipse. Two-beaked loops having equal areas, breadths, and heights can also be made up from portions of any two curves provided that these curves are similar. He thought it would be of value to discuss the harmonics of the magnetising current, as deduced from the statical hysteresis loop, when the flux varied according to laws other than the harmonic law. F. J. Dykes had investigated the law according to which the flux must vary in order that the magnetising current may have a pure sine shape. To find the harmonics of the flux curve in this case and compare them with the harmonics of the current curve in the author's case would be of interest. A practical use of Dr. Thompson's rapid method of analysing the current wave into its harmonics is that it enables us to compute approximately the eddy-current losses in iron in certain cases by utilising J. J. Thomson's and Heaviside's

formulæ.

Dr. W. H. ECCLES, referring to the emphasis laid by Prof. Thompson on the hysteresis ellipse obtained by his ingenious mode of analysis of the hysteresis loop, suggested that other closed curves would be obtained if other normal functions were used in the analysis. In regard to the author's suggestion that his results affected our notions of the phenomenon called hysteresis, he thought no change was needed if we kept the term to its original meaning of a lag in state, in contradistinction to (what is often implied) a lag in time.

A paper entitled "The Energy Relations of certain Detectors used in Wireless Telegraphy," by Dr. W. H. ECCLES, was taken as read.

The paper is a record of the results of an experimental examination into the physical properties of the electrolytic detector, the zincite rectifier, the carborundum rectifier, and a thermoelectric detector consisting of a light contact between graphite and galena. The conditions of the experiments have been generally identical with those arising in the ordinary employment of the detectors, and, in particular, the quantities of energy given to the instruments, in the form of electrical oscillations, have been of the same order in these experiments as in actual practice. Three ways of investigation are followed. The first way consists in applying to the detector an electromotive force which is gradually increased, and measuring the current