matter extracted with dilute sodium hydroxide, the extract being added to the main bulk of the liquid. On rendering slightly alkaline by the addition of concentrated sodium hydroxide solution and keeping the mixture cooled in ice, a pale orange-yellow precipitate was obtained, which, after half an hour, was collected and dried. For analysis a portion was extracted with absolute alcohol several times, and finally crystallised twice from aqueous alcohol: 0.1063 gave 0.2106 CO2 and 0·0505 H2O. C=54·03; H=5·28. 0.1758 181 c.c. N2 at 20·7° and 757 mm. N=11.92.

C16H18O3N3SNa requires C=54·06; H=5·11; N=11·83;

Na 6 47 per cent.

The sodium derivative crystallised in small, flocculent masses, soluble in water, but sparingly so in absolute alcohol. This compound was more easily obtained crystalline than the sodium salt of dibutylaminoazobenzenesulphonic acid.

was re

Sodium 4-mono-n-butylaminoazobenzene-4'-sulphonate duced by means of zinc dust and hydrochloric acid. After filtering off the excess of zinc dust and rendering strongly alkaline with sodium hydroxide solution, the solution was extracted with ether. The addition of alcoholic hydrogen chloride to the ethereal extract gave a white precipitate which crystallised from alcohol in white, shining plates, and was identified as p-phenylenemono-n-butyldiamine dihydrochloride. (Found, Cl=29.98. (Found, Cl=29.98. Calc., Cl=29.90 per cent.) On rendering alkaline, p-phenylenemono-n-butyldiamine was obtained on extraction with ether in white, glistening plates melting at 31° (T., 1917, 111, 1033). After crystallisation from light petroleum, a mixture with a specimen of the base obtained by the reduction of p-nitroso-n-butylaniline melted at the same temperature.

[Received, December 6th, 1917.]

XV.-Studies of Drying Oils. Part I. The Properties of some Cerium Salts obtained from Drying

Oils.

By ROBERT SELBY MORRELL.

CEROUS salts of a number of organic acids have been described by Rimbach and Kilian (Annalen, 1909, 368, 110), Morgan and Cahen (T., 1907, 91, 477), Biltz (Zeitsch. anorg. Chem., 1905, 45,

89; Annalen, 1904, 331, 334), and Levy ("Chemistry of the Rare Earths," 134).

The autoxidation of the cerous compounds has been investigated by Baur (Zeitsch. anorg. Chem., 1897, 13, 251; Ber., 1903, 36, 2658), Job (Ann. Chim. Phys., 1900, [vii], 20, 205), and Engler (Ber., 1902, 35, 2642), and the catalytic activity of the ceric and cerous salts has been discussed by Barbieri (Atti R. Accad. Lincei, 1907, [v], 15, i, 395, 399).

In view of the large proportion of cerite earths in monazite sand it seemed advisable to investigate the properties of cerous and ceric salts of aliphatic acids of the C16 and C18 series, with special reference to their solubility in solvents and to the catalytic activity of the contained metal.

The general methods of preparation of cerous salts of organic acids are:

(1) By the action of acid on freshly precipitated cerous carbonate.

(2) By the interaction of a soluble cerous salt and the potassium salt of the corresponding acid.

The first method leads to the formation of acid salts of the type X3Ce,X, the second to the production of salts of the normal type, CeX3 (Rimbach and Kilian, loc. cit.) [X= acidic radicle].

In this paper the cerous salts of the following acids have been prepared and their properties investigated: palmitic, stearic, oleic, elaidic, linoleic, a- and B-elæostearic, linolenic, and abietic acids.

The method of preparation of the normal salts has been employed, and it must be pointed out that special precautions must be taken to ensure satisfactory neutralisation, otherwise the precipitated salts may be contaminated with excess of either acid or cerium.

All the salts are colourless and insoluble in water.

Cerous stearate, elaidate, B-elæostearate, and palmitate are insoluble in ether. When freshly prepared, cerous oleate, linoleate, linolenate, a-elæostearate, and abietate are readily soluble in ether or turpentine. Cerous palmitate and stearate, like the corresponding lead salts, are insoluble in turpentine.

No suitable solvents could be found from which the salts could be satisfactorily crystallised. In the case of acids forming cerous salts insoluble in ether, the granular precipitate was analysed directly, but where the salt was soluble the ethereal solution was concentrated and the solid salt obtained thereby was analysed. In all cases the salts were of the normal type CeX。.

The ethereal solutions of the cerous salts of the unsaturated acids darken on keeping or on exposure to air and, in the case of the

linolenate, a buff-coloured precipitate having a peroxide reaction separates, corresponding with CeO(XO2)2, basic ceric oxylinolenate, and the brown ethereal solution would appear to contain a mixture of CeX, and CeX or CeX ̧+502= 2CeO(XO2)2+2CeX4.*

Cerous oleate in ether gives, on exposure, a slight turbidity, and the solution changes only slightly towards the dark brown colour of ethereal cerous and ceric linolenates.

In an investigation of the changes which occur when drying oils are polymerised by heat (Morrell, J. Soc. Chem. Ind., 1915, 34, 105), it was pointed out that there was evidence of the shifting of intramolecular linkings prior to polymerisation.

The marked differences with regard to the insolubility in ether between cerous oleate and elaidate and cerous a- and B-elæostearates suggested that differences might be observed in the cerous salts obtained from the various thickened oils, which would give further support to the idea of change of linking.

From olive oil were obtained cerous salts of the normal type CeX, soluble in ether and passing only slowly into an insoluble, CeOX2, type. When the olive oil is heated out of contact with the air (Morrell, loc. cit.), part of it (barium salt insoluble in ether or a mixture of benzene and alcohol) is of the normal type, but the barium salt soluble in a mixture of benzene and alcohol gives a soluble salt of the CeX, type and an insoluble basic ceric salt, CeOX2. The olive oil underwent no polymerisation during the heating.

From poppy-seed oil, heated under the same conditions and containing no polymerised compound, similar cerium salts of the types CeX, and CeOX2 were obtained. The original poppy-seed oil gave a salt of the normal CeX, type.

From thickened linseed oil after the removal of the polymerised substance by means of acetone the yield of basic ceric salt, CeOX2, increased to nearly 50 per cent. A blank experiment with untreated linseed oil gave the normal CeX, and only 12.4 per cent. of a ceric salt of the CeO(XO2)2 or CeO(XO4)2 type.

The results of these experiments do not indicate conclusively that changes in linking have occurred, although full precautions were taken to avoid oxidation during the heating of the oils and in the preparation of the cerium salts. The probability of oxidation is too great to be ignored; nevertheless, in olive oil the presence of two glyceride modifications is indicated; one yielding, after heating, the normal type of cerium salt, whilst the second gives an oxidised type of cerium salt showing the existence in the oil of

* On free exposure to air, an insoluble salt of the type CeO[XO.]1⁄2 was obtained.

modifications with different properties. Applying this view to poppy-seed and linseed oil and with due consideration to chances of oxidation and formation of mixed cerium salts, there remain grounds for belief that during the thickening of poppy-seed and linseed oil changes of linking occur with the formation of modifications which on continued heating out of contact with air are polymerisable.

The properties of the cerium salts from thickened linseed oil (soluble in acetone), on the whole, resemble those from thickened poppy-seed oil, which is to be expected as the linolenic glyceride has been removed from the linseed oil by acetone after the thickening.

It seemed advisable to investigate the cause of the change in solubility without change in colour observed in certain cerium salts (for example, cerous a-elæostearate) after treatment with ether. Since the possibility of oxidation could not be decided by a cerium estimation, cerium a-elæostearate was transformed into the corresponding acid, which was examined for evidences of oxidation.

The experimental difficulties lie in the fact that China wood oil, in addition to small quantities of oleic acid and B-elæostearic acid, often contains oxidised acids, as shown by the liberation of iodine from potassium iodide: in marked contrast to linseed oil, which liberates comparatively a smaller amount of iodine.

It was found that the freshly prepared salt, readily soluble in ether, gave an acid with the melting point and high iodine value of a-elæostearic acid, but the salt, formerly soluble, and afterwards insoluble in ether, yielded a mixture of a crystalline acid melting at 45-46° and having an iodine value of 177·8, and a syrupy acid with a lower iodine value and varying iodine-liberation value.

Lead a-elæostearate was found to give 25 per cent. of a salt soluble in ether, containing an oxidised acid, and the insoluble part furnished a good yield of an acid melting at 44°.

The conclusion drawn from the experiments is that partial oxidations have occurred in spite of all precautions taken, although the cerium a-salt in ethereal solution gave no precipitate when air or oxygen was passed through it.

The occurrence of mixed unoxidised and oxidised acid in the insoluble salt can only be accounted for by the formation of an insoluble basic ceric salt of the type CeXO (Ce=14·1) and subsequent partial oxidation of the acid, although no decided colour change characteristic of ceric salts was observed. No appreciable amount of B-elæostearic acid was identified, so that stereoisomeric change had not occurred. If this is not admitted, then a change in the form of the cerium salt must have occurred without the pro

duction of isomerism in the acid radicle. The evidence, on the whole, supports the theory of the formation of a basic ceric salt with subsequent partial oxidation of the acid radicle.

The rate of absorption of oxygen by cerous a-elæostearate shewed that half the amount of oxygen was absorbed in the first day, whilst more than ten days were required before the salt became approximately constant in weight.

The study of the oxygen absorption of the salt was easy to follow, and showed that with the formation of a basic ceric a-elæostearate of the type Ce2O(XO2)6, from CeX, or CeXO, one molecule of oxygen per molecule of acid was absorbed or that only one double linking was affected, so that the iodine value and the iodineliberation value became approximately equal. It was only after a year's exposure to oxygen that the second double linking of elæostearic acid was peroxidised.

The peroxidic acid showed gradual polymerisation until the syrupy acid set to a varnish. It had all the properties of peroxidic acids described by Harries, namely, instability in the presence of alkalis, but stability towards dilute acids, and was not reduced by zinc dust and acetic acid.

The investigation of these peroxidic acids will be continued because the study of them will go far to elucidate the problem of drying oils.

Another interesting result was the indication of the presence of the B-acid among the products of oxidation of cerous a-elæostearate. B-Elæostearic acid is less easily oxidised than the a-modification, and can be separated from the mixed acids, as it is soluble in light petroleum whilst the peroxidic acid is insoluble. The yield of the acid is small, not more than 10 per cent., and, moreover, its potassium salt is comparatively stable in air. At present it must be regarded as a component of the sample of the original oil, although its cerium salt is sparingly soluble in ether and only the salt soluble in ether was employed.

The change of the a-glyceride into the B-glyceride has already been investigated (Morrell, T., 1912, 101, 2082), and in a later communication the transformation of the a-methyl ester into the B-ester will be described.

From the results stated, the author is inclined to consider that, in drying oils, oxidation to peroxidic acids is followed by polymerisation. This polymerisation may be accelerated by other agents, which would account for a common practical use of two different driers, one essential for oxidation and the other for accelerating the subsequent polymerisation.