CHEMICAL NEWS,}

July 23, 1909

These results, as a whole, are hardly as good as those obtained with the graphite dish, and, like those, an occasional one was bad. The errors observed in the case of the Classen dish are doubtless due to hurried and perhaps careless manipulation. It may be noticed, moreover, that in the case of the graphite dish the results are mostly low, while in that of the platinum they are sometimes high and sometimes low.

In Table IV. the results obtained with the Classen dish are tabulated against those obtained with the graphite dish.

The results obtained for the graphite dish, as set forth in this table, are for the most part likewise lower than those obtained with the platinum dish. It appears that there is perhaps some loss in the weight of the dish itself in drying which causes the low results. Therefore, the method of drying directly over the flame will be abandoned, and instead the dishes will be washed thoroughly with distilled water and then dried rapidly in a stream of warm dry air.

The dishes are now being tested in actual analytical work. Known volumes of a standard copper solution are being analysed in them with rotating anode and at high current density. This will be considered a crucial test, and not until the results of this test are known can the dish be unqualifiedly recommended. This paper is therefore merely a preliminary note. No further tests are needed, however, we feel, to show that it may be substituted profitably in numerous electrochemical operations where the Classen dish has been employed heretofore, or would have been had it been a less expensive article.

These dishes have been suggested for use in other operations not connected with electrolysis, such as digestions in hydrofluoric acid at high temperatures. In such cases the beaker shape would probably be advantageous.

A rotating graphite anode has been designed to accompany the dishes. This is constructed after the general plan of the platinum anode described by Miss Langness Fourn. Am. Chem. Soc., 1907, xxix., 459). It is dishshaped and contains radial slits in its walls and a circular opening in its bottom. It is hoped that by means of it

45

the interesting results obtained with the anode referred to above may be duplicated.

Work is now being carried on, as intimated above, to show the limiting capabilities of the graphite cathode dish (manufactured and on sale by Eimer and Amend, New York). A further report, therefore, will be made. The efficacy of the dish in numerous electrochemical separations and operations will also be determined. It is also our intention to investigate the rotating dish anode referred to above, and a smaller disc-shaped rotating anode with a graphite stem.

Summary.

1. Simple graphite electrodes are described which are designed for use in the place of platinum as insoluble electrodes in electrochemical experiments.

2. An account is given of preliminary experiments with a graphite dish intended to supplant in some forms of electrochemical analysis the Classen platinum dish.

3. The dish is recommended for electrochemical separations and for analyses where great accuracy is not required. Confidence is felt that, after it has been further developed, it will be able to entirely take the place of the platinum cathode dish.

THE CHEMISTRY OF SYNTHETIC CAMPHOR. By WILLIAM A. DARRAH, B.S.

THE list of those compounds for the supply of which commerce has been forced to rely upon nature is being rapidly shortened; perhaps the latest substance to be synthetically produced is camphor, which, while it is an article to be found in every household, has only recently been produced by manufacturing methods on a scale to successfully compete with the natural supply.

The term "synthethic" as applied to a chemical compound is commonly and most erroneously confused with "artificial"; though the difference is very great, particularly in the case of camphor. As correctly used the term "synthetic compound is one produced by man though having exactly the same properties and constitution as the natural article. On the other hand, in the arts, the term "artificial" denotes an imitation of a natural product, which, while possessing some of the peculiarities of the substance from nature is yet essentially different.

This is well illustrated by the case of camphor, as it happens that the two terms are used in the camphor trade for different substances. As previously stated synthetic camphor is identical with common or Japan camphor, while artificial camphor, while resembling the natural in smell and general physical appearance, is chemically quite distinct. Thus Fig. 1 shows the formula of camphor, while the constitution of artificial camphor is given in Fig. 2.

With the view of analysing the development of the recent synthetic process, and to show the imperative need for such, it may be of interest to touch in a general way upon the occurrence and extraction of natural camphor. This is practically all derived from the juice of a tree closely related to our common laurel, but which grows to very much larger sizes. This tree, the Larus camphora, thrives best in the warm moist climates of southern China and Japan, from which part of the world the great portion of the natural supply is obtained. While the name common or "Japan camphor discloses the largest producer, yet Java, Borneo, Sumatra, and the neighbouring islands are the source of a large part of the world's supply.

The natural process of extracting camphor is simplicity itself, and is as inefficient as it is simple. The substance occurs as small drops or "tears disposed between the fibres of the wood, the root being particularly rich in camphor. The trees of Borneo and Sumatra contain comparatively large tears, which are extracted by the

natives after splitting the felled tree with crude wooden wedges. As thus obtained, the substance is fairly pure.

The trees of China and Japan, on the other hand, contain a larger number of much smaller deposits, more widely distributed, thus necessitating a more complicated process of extraction. The tree is first cut up into a number of small blocks or wedges about two inches upon a side, the faces being so chosen that the greatest amount of fibre end is exposed. To facilitate this the blocks are sometimes shredded.

Now camphor is very volatile at ordinary temperatures, it being one of those substances which at ordinary pressures will vaporise before melting. Therefore while the melting-point of camphor is twice that at which water boils, yet when the fibres of the camphor tree are heated in large vats of boiling water and the vapours are condensed, it is found that practically all of the camphor is removed, though in a very impure state. The preceding steps are usually carried out in Japan or China, where the trees abound and labour is cheap, while the final purification is done in Europe, Germany and England being the largest refiners.

Previous to transportation the camphor distillate is filtered through straw and brush matworks, which separate the flocculent camphor. The filtrate is pressed to exclude the excess of water, thus leaving the crude camphor in the

form of large impure cakes, in which shape it is exported. The further steps are the final purification, which consists essentially in fractional distillations, advantage being again taken of the ease with which the substance volatilises.

The most casual analysis of the above process reveals one of the inherent and insurmountable defects, namely, the whole tree is destroyed in the process of extraction. Now each tree yields on an average only 20 pounds of camphor, while it requires approximately thirty years in which to mature. It must be evident therefore that for this reason the natural supply of camphor is kept within very narrow limits, thus giving one very important stimulus to synthetic production.

an analyser similar to the saccharometer used in the sugar industries. On comparing the rotary power of the specimen with a known standard from the same cake, the percentage of camphor may readily be determined. As an ingredient in many patent medicines, as a preservative, and as the starting-point in the synthesis of numerous compounds, camphor has an enormous yearly consumption. Here is, therefore, the second powerful force acting toward the development of a synthetic process. Perhaps the determining cause, however, certainly an important factor in the situation, is the fact that the natural supply of camphor is monopolised by Japan, who naturally exacts a monopoly price for the product. These three causes combine to make the synthetic production of camphor profitable. First, the large and increasing demand; second, the limited supply; third, the present monopoly of the natural article. As a result synthetic camphor has recently been introduced, and is now being manufactured on a commercial scale.

The synthesis consists of six steps, but before entering upon the details it is of interest to trace the logical development of the process.

In making a survey of the possible sources from which camphor might be commercially synthesised several requirements must be kept in mind. The raw material must be cheap. It must be plentiful. It must be as closely related to camphor as possible, thereby reducing the amount of work required in the transformation to the minimum.

The compound which most nearly fits these requirements is pinene, which, as the chief constituent of turpentine oil, is both plentiful and cheap, while structurally it is closely allied to camphor. In fact, the closeness of this relation has led to previous attempts to devise a synthetic process. One notable instance of an unsuccessful trial was made at Ampere, N.J., and only failed after a determined effort to make a laboratory method commercial.

The first step in the procedure at present being used is the preparation of the pinene, by the fractional distillation of turpentine; that part which boils between 155° and 160° being 90 per cent pinene, which is the principal constituent of turpentine. The formula of this substance is shown in Fig. 3. It will be noted that it is double ring, aromatic, unsaturated hydrocarbon, closely related to camphor.

The distillate thus obtained is cooled and saturated with anhydrous hydrochloric acid, which transforms it from a clear transparent liquid to a white crystalline mass. This substance is pinene hydrochloride, known technically as artificial camphor, for reasons previously mentioned. It is interesting to note the shifting of the ring formation from that characteristic of pinene to that of camphene. The addition of the hydrochloric acid is therefore an expedient by means of which the ring formation is altered, and the double bond of unsaturation removed, for when, as in the next step, the acid is removed, not the original pinene but an isomer, camphene, is obtained. As shown graphically in Fig. 3 the structural formula is now more similar to camphor. It will be noted that the double bond, the point at which a compound is most open to attack, is now so placed that the addition of oxygen at the required point is a comparatively simple matter.

The removal of the hydrochloric acid may be accomplished by adding any substance having a stronger affinity for the acid than the pinene hydrochloride, and not possessing any radical to give in return. Three practical methods have been devised, namely:(a). Heating with ammonia (NH3), amines (NH2),

CHEMICAL NEWS,}

July 23, 1909

oxidise an organic compound directly without destroying the substance; however, some other radical may be first added, and an oxygen atom then substituted. This is the process followed in this case.

The camphene previously formed is dissolved in its own volume of glacial acetic acid, and 5 per cent of fuming hydrochloric acid added. The product thus formed is isobornyl acetate, an oil boiling at 225°, but, like camphor, volatile with steam. The structure is shown graphically in Fig. 3.

It now only remains to replace the acid radical by oxygen, and the process is complete. This is done in two steps. Since sodium hydrate has a stronger affinity for the acid than the isobornyl acetate, it might be expected that in the presence of this base the acetic acid would be separated; and such is the case. On adding a concentrated solution of sodium hydrate borneol is formed, and also a by-product of sodium acetate. A glance at the structure shows that when the OH or hydroxyl grouping of the borneol is replaced by oxygen, thus forming a ketone compound, the process is complete.

Such a secondary alcohol is readily oxidised, chlorine, oxygen, ozone, nitric acid, and a wide range of other oxidising substances being available. Chlorine is commonly employed in practice, and the yield, while not theoretical, is very satisfactory from a commercial standpoint. The product thus obtained is purified by sublimation, after which it is put upon the market. With two exceptions the synthesised product is identical with the natural. The exceptions are, first, the synthetic camphor is purer than the common variety, and, second, the laboratory camphor is of the racemic type (i.e., it is not optically active), due to the fact that equal quantities of dextro- and lævo-rotatory camphor are produced.-The Chemical Engineer, 1909, ix., 163.

PROCEEDINGS OF SOCIETIES.

FARADAY SOCIETY. Ordinary Meeting, June 29th, 1909.

Dr. N. T. M. WILSMORE in the Chair.

DR. HENRY J. S. SAND read a paper entitled "Apparatus for the Rapid Electro-Analytical Separation of Metals." The paper contains a description of some developments made in the apparatus, first described by the author about two years ago, for the rapid electro-analytical deposition and separation of metals (Chem. Soc. Trans., 1907, xci., 373; also Trans., 1908, xciii., 1572). This apparatus for the first time combined in a practical manner the use of an auxiliary electrode and very rapid stirring of the electrolyte, and made it possible, as has been shown so far, to deposit and separate from each other for purposes of chemical analysis the metals silver, mercury, copper, bismuth, lead, cadmium, zinc, antimony, and tin. The times required for these depositions varied in the majority of cases between five and fifteen minutes. Apart from the very high stirring efficiency of the electrodes the apparatus is believed to be superior to others of similar type in the exceedingly great simplicity of the method of making and undoing the electrical connections on a single stand, in the fact that the electrodes may be used with ordinary beakers, and in the simple manner in which the electrodes may be washed and dried. No alterations in principle have therefore been made to the apparatus, but the following additions and simplifications are described.

As hitherto, a mercury contact has been employed in the electrolytic stand to make the connection between the stationary and the moving parts; a special screw cap has, however, now been provided, which may be screwed down when the apparatus is not in use, making it possible to transport it without taking out the mercury.

47

A clutch arrangement has been added which enables the operator to start or stop the rotation of the anode without stopping the motor. Such an arrangement will be found of advantage if it is desired to actuate several sets of apparatus from one shaft driven by a single motor; or if the current is obtained from a small motor-generator which is also employed for rotating the electrode, the clutch making it possible to stop or start the stirrer without stopping the current; or lastly, if a hot air or water motor is employed which cannot be stopped instantly during the washing of the electrodes.

A very considerable simplification has been obtained by fitting all the apparatus required for the measurement of the potential of the electrode in a single box. The arrangement has been designed so that by depressing a key it will also allow the potential difference between the anode and the cathode to be read directly. It was thought very desirable to retain the capillary electrometer as a zero instrument, but it became necessary to design a new portable form suitable for the purpose in view. It may be described as a closed evacuated form developed from the Ostwald horizontal capillary electrometer. It is provided with an enclosed scale, and if observed by a lens of small magnification it will readily indicate 1 millivolt.

Dr. B. BECKETT DENISON communicated a paper entitled "Researches on the Relative Rates of Migration of Ions in Aqueous Solution."

The author has determined by the method of direct observation of moving ionic boundaries the transport numbers of the halide salts of the metals of the alkalis and alkaline earths. The concentrations of the solutions were O'I to 0.02 normal. It is pointed out that the study of transport numbers by the direct and indirect methods has been shown to afford a means of determining the degree of hydration of the ions, although in the present paper no degrees of hydration were calculated.

Prof. R. ABEGG (communicated) congratulated the author on having succeeded in filling the gap of electro-chemical constants of so important a group of ions as the halides.

Mr. S. FIELD read in abstract a paper on "The Conditions which determine the Composition of Electro-deposited Alloys. Part I. Copper-zinc Alloys."

ditions as

As a result of a large number of experiments on the electrolytic deposition of brass, the author has, by the analysis of the deposits, shown the regular manner in which the composition changes with such varying con(1) proportion of copper and zinc compounds in the solution; (2) strength of the solution; (3) temperature; (4) current density; and (5) the presence of free cyanide. It is thus shown that the proportion of zinc is increased (a) at lower temperatures; (b) with more dilute solutions; (c) with increased current density; and (d) by the absence of free cyanide. With a large proportion of zinc compound copper is still freely deposited. The author incidentally draws attention to a number of important conditions which primarily affect the composition of the solution, and ultimately the character and composition of the deposit. The work is being continued on other binary alloys.

graphy is given, and for this alone the book will be of much assistance to the metallurgist. Every part of the book is thoroughly systematic, and great use is made of tabular schemes and classifications, which give a large amount of detailed information in a concise form. For instance, the extraction of the metal from its ores by various processes is tabulated in such a way as to show at a glance the outlines and essential points of the different processes.

Le Materia Radiante e I Raggi Magnetici. ("Radiant Matter and the Magnetic Rays "). By AUGUSTO RIGHI. Bologna: Nicola Zanichelli. 1909.

A SHORT account of recent research on radiant matter is given in this book, which is very lucidly written. Very little mathematics is introduced in the text, the formulæ relating to the motion of an electron in a uniform magnetic field, &c., being worked out in an appendix. Discharge in a magnetic field is treated comparatively fully, and the book gives an excellent short summary of the present state of our knowledge of radiant matter and magnetic rays. CHEMICAL NOTICES FROM FOREIGN SOURCES.

Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences. Vol. cxlviii., No. 23, June 7, 1909. Preparation of the three Oxy and of the p-Dimethylamido- and Diethylamido-benzylidene Camphors, and of the p- and m-Tolylidene Camphors.-A. Haller and Ed. Bauer.-The o, m, and p-oxybenzylidene camphors may be prepared by the condensation of the three oxyaldehydes with camphor in presence of soda; p-dimethylamido and diethylamido benzylidene camphors are formed when the respective aldehydes are added in small quantities to an ethereal solution of camphor and soda, and the tolylidene derivatives similarly. The three oxy derivatives are colourless like benzylidene camphor itself, but their solutions in alkalis are more or less dark

yellow. The specific rotatory power of these compounds in alcoholic solution is of the same order of magnitude as that of benzylidene camphor and the methoxybenzylidene camphors, though somewhat higher. The specific rotatory power increases as we pass from the meta and ortho to the para derivative. The specific rotatory power of the oxy derivative is higher when an alkaline solution is used. The dialkylamido derivatives are yellow, and give with acids, especially hydrochloric acid, colourless salts which are dissociated by water. These basic compounds have a much higher specific rotatory power than the oxy derivatives, and this power is much diminished by the addition of acids.

Chemical Reactions in Gaseous Mixtures subjected to very great Pressures. E. Briner and A. Wroczynski. Under very great pressure, and at the temperature of liquid air, the system NOHCl condenses to a dark red-violet solid which is undoubtedly an addition product. At the ordinary temperature this compound disappears, and the mixture becomes colourless, and after a time two layers of liquid appear, one light red and the other light yellow. The former is nitrosyl chloride, and the latter is water containing NOCI. The reaction occurs according to the equation 2NO+ 2HCl = NOCI + H2O + ¿Cl2 + ¿N2. The system NO-SO2 yields, under the same conditions, a pale green solid which is stable at the ordinary pressure and appears to be a mixed anhydride.

Hydrated Compounds of Thorium Chloride with Alkaline Chlorides.-Ed. Chauvenet.-The author has prepared the following double compounds of thorium and alkaline chlorides: ThC14. LiCl.8H2O, ThC14. NaCl. 10H2O, ThC14.KC1.9H2O, ThC14.2RbC1.9H2O, ThC14.2CsC1.8H20, ThC14.2NH4Cl. 10H2O. Thermic determinations show that the hydrates given by Li, Na, and K are more stable than those formed with Rb and Cs. The hydrates of the

chlorides of the three first metals are much less stable than the anhydrous chlorides, and much more stable as hydrates than those of the two last. Hence when the double hydrates of Li, Na, and K are dehydrated even in a current of hydrochloric acid a high temperature has to be used, and then the H2O reacts to give oxyhaloids. Possibly at higher temperatures these oxyhaloids, Th(OH)Cl3. MCI, would give ThOCl2. LiCl, ThOCl2. NaCl, ThOCl2.KCI, and at a still higher tempera

ture Tho2+ ThCl4 + 2LiCl, ThO2 + ThCl4 + 2NaCl, | ThO2+ ThCl4 +2KCİ. This prediction has been verified for ThOHC13. LiCI.

Normal Butene and some Derivatives.-Georges Dupont.-Very good yields of normal butene can be obtained by dehydrating normal butyl alcohol with aluminium, absorbing the butylene by bromine, and decomposing the bromide by means of caustic potash at 180°. The volatile butene then distils over. Pure butene is a liquid which boils at 18.5°, and solidifies at - 130°. With bromine it gives the dibromide, C2H5-CBr = CHBr, and a crystalline tetrabromide. From the cuprous derivative octadiine, C2H5—C=C—C=C—C2H5, can be prepared, and various syntheses can be effected by means of the magnesium derivative of butene bromide.

Synthesis of Derivatives of Racemic Fenone.MM. Bouveault and Levallois.-The authors have previously described the preparation of an amide which has the composition of racemic dihydrofencholene amide, but has a lower melting-point. Hypobromite acts on dihydrofencholamide, a derivative of natural fenone, giving a symmetrical urea, diapofenchylurea, and with the racemic amide, obtained by mixing the two active amides, two symmetrical isomeric ureas are formed. The synthetic amide also gives two isomeric ureas. equal parts of the enantiomorphic ureas gives the racemic

urea.

MISCELLANEOUS.

A mixture of two

will be given at the Institute for Microscopy of the Jena Series of Lectures on Scientific Microscopy.-These University from October 11th to 16th, 1909. The microCarl Zeiss (Jena) Optical Works. The following is the scopes and apparatus are lent for the occasion by Messrs. syllabus of lectures, demonstrations, and practical lessons:

October 11th-Dr. H. Ambronn: Lecture "On Abbe's

Theory of the Formation of the Microscopic Image." Practical Lessons with the Diffraction Apparatus after Abbe.

October 12th-Dr. H. Ambronn: Lecture on "The Method of Testing Objective Systems." Practical Lessons with the Abbe Test Plate and the Abbe Apertometer.

October 13-Dr. H. Siedentopf: Lecture on "Dark Ground Illumination." Practical Lessons in Dark Ground Illumination.

October 14-Dr. A. Köhler: Lecture with Demonstration on Photomicrography. (a) Projection of the Image on the Plate. (b) Illumination of the Object with Transmitted and Incident Light." (Vertical Illuminator).

October 15th-Dr. A. Köhler: Lecture on "Photomicrography with Ultra Violet Light." Dr. H. Siedentopf: Lecture on "Ultramicroscopy."

October 16th-Demonstration relating to the Lectures delivered on the previous day. (a) "Photomicrography with Ultra Violet Light; (b) with Monochromatic Visible Light; (c) with Incident Light (Vertical Illuminator) for Metallography; (d) Ultramicroscopy of Firm Colloids; (e) Ultramicroscopy of Colloidal Solutions; (f) Ultramicroscopy of Cells and Fibres."

Application for admission to the above Course of Lectures should be sent to Herrn Dr. EHLERS, Beethovenstr. No. 14, Jena.

Successors./

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