Alkaloids of the Australian Rutaceae: Acronychia baueri. II. Some Reactions of the Alkaloid Acronycine

Acronycine, C20H19O3N, is readily converted to noracroaycine, C19H17O3N, a weak base which contains no methoxyl. Acronycine contains a reactive double bond, shown to be present in a dimethylpyran ring by oxidation to an acid which, on heating, yields α-hydroxyisobutyric acid together with a phenol, Cl4H11O3N, and its methyl ether, Cl5H1303N. The action of alcoholic potash on acronycine results in the formation of two phenols, both of which are readily reconverted to acronycine. The bromination of acronycine has also been studied.

Rubber Photogels. II.

In a previous communication the writer has shown that the formation of gels from rubber sols on irradiation is often accompanied by an increase in weight so that the solvent and (or) sensitizer apparently reacts photochemically with the solute. The increase in weight of the rubber after removal of the solvent was found to be greater the more rapid the gelation of the sol. It was suggested that this increase in weight might result from products formed by reaction between the solvent and sensitizers independently of the rubber; the product in that case might be rubber physically associated with such photochemical products. This seemed unlikely, as prolonged extraction of the moist or dried photogels with acetone and alcoholic potash removed only a part of the increase. As a further check, a mixture of solvents and sensitizers without rubber was irradiated in sealed tubes and the products were examined. These experiments have been repeated by exposure to sunlight in a window with southern aspect for a whole year. In some cases small quantities of nonvolatile substances were obtained, but these were readily soluble in acetone and, therefore, did not account for the increase in weight, or at least for only a small part of it, and that part was acetone-soluble. It appears, therefore, that any reaction which takes place on insolation between the solvents, with or without additional sensitizers, cannot account for the observed increase in weight of dried photogels. The conclusion is reached that a photosynthesis has taken place, and that the gels consist of a rubber reaction product, at least where an increase in weight takes place.

Studies on carotene in relation to animal nutrition: Part I. The technique of carotene estimation in feeding stuffs

A modified method of estimating the carotene content of plant material has been described in detail. The modifications include a combined aqueous and alcoholic potash hydrolysis of the original material before extraction is carried out.A statistical analysis and a recovery test have shown this method to be relatively more efficient than methods similar to those described by other workers.

Studies on the Acetone Extraction of Raw Rubber

(1) For the determination of the saponification value of the acetone extract, 20 cc. 0.2 N alcoholic potash is added to the extract and the flask is heated on a water bath for 60 minutes. It is then titrated with 0.1 N HCl solution, using phenolphthalein as indicator. (2) When the saponification values of the acetone extracts of 8, 16, and 24 hours are compared, the saponification value of the 8 hour extract is seen to be high, while those of 16 and 24 hour extracts are low. This indicates (a) that the 8 hour extract contains a higher percentage of saponifiable matter than the 16 and 24 hour extracts; (b) the quantity of rubber hydrocarbon which is dissolved in the acetone extract increases with increasing time of extraction, and (c) the acid value of the acetone extract decreases during the period of extraction from 16 to 24 hours. (3) Regarding the saponification values (R) of the acetone extracts of 8, 16, and 24 hours, similar remarks may be made as in (2) above.

Alcoholic Potash Extraction of Vulcanized Rubber

In the analysis of vulcanized rubber, the estimation of matter extractable by alcoholic potash solution has long been applied, chiefly as a means of detecting and estimating factice. The test was originally made by weighing the rubber before and after boiling with potash solution, the loss in weight being taken as representing the factice content (cf. Weber, The Chemistry of India Rubber, London, 1919, page 245). Though this method has now been generally superseded by that in which the extract is acidified and the resulting fatty acids are extracted with ether and weighed, the older “loss in weight” method is still prescribed in some specifications for rubber goods. It has long been recognized that the loss in weight is not an accurate measure of the factice content for the following reasons: (1) it is difficult to remove all the potash from the extracted rubber before weighing it (cf. Henriques, Chem.-Ztg. 18, 411(1894)), and (2) the potash extracts part of some mineral compounding ingredients, such as zinc oxide, litharge, and antimony sulfide (cf. Ditmar, Die Analyse des Kautschuks, Vienna, 1909, page 205). It has been found that another possible source of serious errors in the “loss in weight” method is the action of the potash on light magnesium carbonate. If magnesium carbonate is boiled with alcoholic potash solution, it loses a considerable amount of its combined carbon dioxide and/or water. Thus in an experiment where 0.3 gram of the carbonate was boiled for 6 hours with 60 cc. of potash solution (KOH 5 g., water 5 cc., absolute alcohol 100 cc.), and then washed with alcohol, dried in vacuo and weighed, it was found to have lost 29.4 per cent of its weight. By igniting the residue to magnesium oxide, it was shown that the potash had not dissolved out any magnesium compounds, so that the loss in weight must be attributed entirely to loss of carbon dioxide and/or water.

The Nature of Vulcanization. Part IV (Continued)

In a previous communication the authors have discussed the limiting figure for combined sulfur in vulcanized rubber, and shown that under suitable circumstances the coefficient of vulcanization can exceed the figure of 47, which is that required by the formula C5H3S. It was thought that the combined sulfur in excess of this amount resulted from the substitution of sulfur for hydrogen. (Further information on this point will be found in the second part of this paper.) In the course of these experiments use was made of the ether-hydrochloric acid extraction method for the removal of mineral sulfides in soft vulcanized rubber. It was thought that this extraction method might not be suitable for use with vulcanites, since the amount of swelling produced by the ether was relatively inappreciable, and consequently the metallic sulfides were not necessarily decomposed. It was also thought that the acid mixture might react with a part of the rubber sulfide and result in a lower coefficient, which would depend on the time of extraction. It is known that vulcanite can be decomposed by the action of alcoholic potash, and the combined sulfur has been reduced in some cases to 26 per cent. It is reasonable to suppose that decomposition takes place in the presence of concentrated hydrochloric acid. In order to determine the extent to which the sulfide is decomposed by the action of the acid a series of extractions was made.

Early Stages of Oxidation in Rubber. A Quantitative Application of the Pyrrole Test

The foregoing will illustrate some of the applications which have been made with the test as developed by the authors. Since the above work was completed, van Rossem and Dekker (5) have published their very significant paper on extraction of rubber with benzene—alcoholic potash mixture. Both methods apply to rubber at the same stage of its life, and it should be interesting to compare results from the same sample. In general it may seem that their method is of somewhat higher accuracy, while the pyrrole test requires less time and labor and is more informative as to the actual processes of oxidation.