name of heliotropin. Investigations by the author have facilitated this conversion and very considerably reduced the cost of production of heliotropin.

The conversion of safrol to vanallin by treatment with sodium methylate and subsequent oxidation is also interesting; the chief source of vanillin is, however, eugenol, obtained from oil of cloves. Eugenol is associated in oil of cloves with a sesqui-terpene, cariophylene, from which the author has recently obtained an acid containing eleven carbon atoms.

(III) A process of expression is used for the extraction of oils which are decomposed by steam, such as bergamot (linalool acetate). The artificial preparation of this ester presents considerable difficulties, as linalool undergoes decomposition or isomerisation on coming in contact with acids and gives only very small yields of the desired esters, but investigations by the author have led to its manufacture on a commercial scale. A laboratory method whereby the difficulty may be overcome, worked out by the author, was also described, and consisted in treating a pyridine solution of the alcohol with the required acidyl chloride. The investigator of linalool has hitherto laboured under the difficulty that no solid derivative of this alcohol could be obtained. It is hoped that the author's recent preparation of a crystalline compound of linalool—the hexanitrodiphenylurethane-will be of assistance in this direction. Geraniol, an isomer of linalool, is important as the chief ingredient of otto of rose. Its acetic and butyric esters are also valuable as scents.

(IV) A fourth and very ancient method for the extraction of essential oils is illustrated by jasmine oil, which is obtained by exposing the flowers over odourless petroleum, whereby the perfume is absorbed and subsequently extracted with acetone. This oil is a mixture of a number of compounds, the distinctive odour being, however, due to jasmone, which is present to only a small extent in the oil. "Peach oil contains also a large number of constituents; among these the author has isolated the ethyl ester of an undecylenic acid, the presence of which is interesting as being a case of the natural occurrence of a fatty acid containing an odd number of carbon atoms.

The sesquiterpene alcohol, santalol, from sandal-wood oil, irone from orris oil, the oxygenated products from orange oil, lemon oil, and lime oil were briefly discussed. The specimens of these various compounds illustrated their valuable properties as perfumes. A few brief remarks throughout the paper illustrated the costliness of these oils; thus it was shown that about three tons of roses were required to yield 1 lb. of otto, the cost of peach oil is between three and four times as great, whilst to prepare 1 lb. of jasmone about 200 tons of jasmine flowers would be required.

8. The Cholesterol Group. By R. H. PICKARD, D.Sc.

Numerous compounds of the empirical formula CHO have been described and have all at some time been called cholesterins or cholesterols. Only a few of these have been well characterised, and their separate identity requires further proof.

The best known of these compounds, animal cholesterol,' of which the best source is human gallstones, is a very stable compound. The presence of an hydroxyl group, of at least one asymmetric carbon atom, and of an ethylene linking in the cholesterol molecule have been proved. The molecule is composed of a normal chain of nineteen carbon atoms attached to a complex nucleus. Attempts to reduce cholesterol by chemical means were unsuccessful, but a dihydrocholesterol has been separated from human fæces.

9. On Acridines. By Professor A. SENIER, Ph.D.

I. Acridines.

In 1871 Graebe and Caro isolated from crude anthracene a yellow crystalline base, which on account of its irritating action on the skin and mucous membrane was named acridine. The base when in solution exhibited a beautiful blue

fluorescence. The subsequent researches of Graebe, Riedel, and others, led to the view now adopted of its constitution as a heterocyclic anthracene derivative of the formula

The resources of synthetical chemistry were not long in bringing to light methods for building up this interesting fluorophoric molecule from compounds of simpler structure. A phenyl derivative was first obtained and the base itself by Bernthsen and Bender in 1883.

The numerous methods which have led to the formation of acridines may be arranged into two classes-1st, those starting from diphenylamine

and its derivatives; and 2nd, those starting from o-amino-diphenylmethane

As illustrations of the first method may be taken (a) condensation by means of aldehydes, for example formaldehyde :—

and (b) condensation by means of methylene diiodide; a method discovered by Mr. Goodwin and myself. For example, using v-cumidine the following represents the reactions which take place :

The related acridones and thio-acridones furnish an instance of ketonic and enolic tautomerism which it would be interesting to investigate by spectroscopic methods as described by Professor Hartley in his Address to this Section.

Another class of compounds formed from the acridines by the addition of two atoms of hydrogen-acridine hydrides or hydro-acridines' -are very unstable, and on oxidation, even by boiling with water, in some cases lose their hydrogen and revert to the original base. They are not fluorescent, a property characteristic of the acridine ring with its para linking, and may therefore have the struc

ture:

NH

CH2

Mr. Goodwin and I, in an inquiry not yet quite completed, have obtained a similar class of dihalides. We have prepared chlorides, bromides, and iodides of a Na

BNB

hexamethylacridine, -naphthacridine, and -naphthacridine (for notation

a Ca

BC3

see Naphthacridines, below). Like their hydrogen analogues, these compounds are unstable and are not fluorescent. Their constitution is therefore in the case of simple acridines:—

The salts and alkhaloids of the acridines are fluorescent, and may be regarded, following Bernthsen and Bender, as true acridines with pentavalent nitrogen,

thus:

II. Di-Naphthacridines.

The following formulæ represent all the possible di-naphthacridines :

The notation adopted is, I think, more convenient than either that of Graebe, adopted by Ullmann, or that of Strohbach, adopted by Möhlau. The numbering is taken from Möhlau and Haase.

The naphthacridines are obtained by methods analogous to the acridines, including especially the aldehyde and the methylenediiodide reactions with naphthylamines. The naphthacridine of Reed and that just announced by Ullmann, both obtained originally by the use of formaldehyde, I have prepared by the methylenediiodide method. There is every reason to hope that the two unknown types of this group of acridines or derivatives of them will soon be discovered.

III. Phenonaphthacridines.

The phenonaphthacridines have been chiefly investigated by Ullmann. There are three possible types:

The notation is a modification of that which I have suggested for dinaphthacridines, and the numbering is that of Ullmann.

Numerous derivatives of phenonaphthacridines are known, and they all possess the characteristic physiological properties and the fluorescence which characterise acridines generally. The remarkable tendency to the formation of the acridine grouping has recently been shown by Ullmann and Baezner. These inquirers find that alcohol may replace aldehyde in acridine synthesis, oxidation taking place in the course of the reaction.

IV. New Experiments.

Experiments now in progress indicate the possibility of new acridine types and also the generality of the methylene diiodide reaction. With the assistance of Miss Micklethwait I have already obtained fluorescent products indicating the formation of a dianthracridine and a naphthanthacridine and of other acridines not previously obtained by the methylene diiodide method.

10. Sur le Spectre de Self-induction' du Silicium et ses Comparaisons Astronomiques. Par le Comte A. DE GRAMONT, Docteur ès Sciences Physiques.

Plusieurs raies du silicium reconnues dans les spectres stellaires ont été considérées comme caractéristiques d'une haute température, et j'ai cru intéressant d'étudier leur manière de se comporter sous l'influence de la 'self-induction,' et de donner ici la partie du spectre susceptible de comparaisons astronomiques. Les spectrogrammes portaient à la partie supérieure, le spectre d'étincelle condensée ordinaire du silicium obtenu avec une bobine d'induction donnant 15 cm