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R.S.] (WITH WHICH IS INCORPORATED THE "CHEMICAL GAZETTE"), Sixty-eight Years.

Friday, April 28, 1916.

A. BOAKE, ROBERTS, & CO. (LIMITED), JOHN J. CRIFFIN & SONS, LTD.,

NEWS

THE

CHEMICAL

VOL. CXIII., No. 2944.

NEWS.

THE USE OF OZONE FOR CHEMICAL RESEARCH AND INDUSTRIES.

OZONE is a powerful oxidising agent which exists in small quantities in nature, but can be produced artificially to an extent only limited by space and money. So far as the British Empire is concerned Ozone may generally be said to be known to chemists but not recognised. It is the Cinderella of the chemical profession and trade, who (with few exceptions) have been content to ignore it as a practical commercial oxidising agent and to regard its suggested applications as the proposals of cranks. The causes for this attitude are not far to seek; in the first place one must take into account the economic status of the British analytical or industrial chemist as it has existed up to the time of the war; in the second place, very few chemists know much or have been able to acquire information about the electrical production of Ozone, its estimation or its practical uses. Much has been written in the daily Press regarding the status of chemists and their training, and although these are questions outside the sphere of this article, they have an important bearing on the subject from the utilitarian and national points of view.

To our shame it must be said that whilst most of the research work in connection with the practical application of Ozone in chemical industries has been done by a British firm, as usual it is the German chemists and manufacturers (often synonymous terms) who have had the enterprise to make practical use of Ozone, and by so-called "secret 29 processes to flood the markets of the world with certain articles of a better quality than could be obtained in this country. The attitude of the manufacturer here has often been too much in the direction of shying at the capital outlay for an Ozone plant without considering how quickly this may be redeemed by the saving effected in the process. Propositions involving the repayment in two years of the capital sunk have been "turned down" as too expensive, whereas to the men of business they would be termed highly profitable investments. In other cases the status of the works chemist has proved an insuperable barrier to the introduction of any new process by an outside firm. Probably these are some of the things that the war will change, and there are already signs of awakening interest in improved processes in general and in Ozone in particular. The object of this article, therefore, is to stimulate this interest by a general survey of the applications of Ozone to the chemical industry, and to describe some of the Ozone research apparatus and industrial plants which have been evolved as the result of many years' experience.

Applications of Ozone.

Although all chemical applications of Ozone are in the nature of oxidation they may be classified for convenience

as follows:

Although of interest to chemists, and especially to works chemists, these treatments cannot be discussed within the scope of this article, as they each necessitate apparatus of a special nature, differing considerably from the plants which will be afterwards described, and which have been standardised for the strictly chemical applications of Ozone.

(1) Manufacture of Chemical Preparations by Ozone. Ozone can frequently replace other oxidising agents with advantage, giving better, cheaper, and quicker results in the manufacture of many of the more expensive chemicals, such as certain synthetic perfumes and aniline dyes and disinfectants. Among these processes may be noted the preparation of vanillin from isoeugenol, heliotropine from isosafrol, artificial hawthorn from amethol, the oxidation of camphene to camphor, the production of indigo from indol, and the manufacture of iodoform from alcohol and iodide of potassium. Ozone has recently also proved to be of value in the oxidation of impurities in tar oil, the conversion of ferrous into ferric salts, and the production of ozonised petrol for internal combustion engines.

Another field, to which attention may be directed at the present moment, is the use of Ozone in dyeing, for fully developing certain colours and producing or modifying others.

A great deal more work still requires to be done in these directions by practical chemists who have the time or by chemical manufacturers who will place at the disposal of their chemists research apparatus such as are described later. It is only by taking up an investigation of this kind (which has been proved in the laboratory) and working it out systematically on a larger scale that practical commercial results can be obtained and present processes superseded by better ones.

(2) Treatment of Oils, Fats, and Waxes, and similar substances by Ozone.

The processes involved in bleaching, deodorising, refining, and technical oxidising are allied to one another, and in fact in many cases two or even three of the processes may be effected by a single treatment. They all more or less rely for their success on the powerful oxidising influence possessed by Ozone.

The object of bleaching is of course to remove natural colouring matter, such as the green vegetable colour (chlorophyll) and the reddish brown colour of palm oil, or of colours due to age or impurities, such as the dark colour of greases, without injuring or altering the composition or nature of the substance bleached.

Liquids may be bleached by various physical methods, such as the use of coagulants, charcoal, or Fuller's earth, but chemical processes alone have to be employed for the bleaching of solid substances. These processes may be divided broadly into two classes: (1) Reduction and (2) Oxidation. The former is entirely an artificial process, and requires the use of such reagents as hydrogen, sulphur dioxide, sulphurous acid (produced by burning sulphur), hydrosulphites, or sulphoxalates. The latter process, on the other hand, is constantly taking place in nature, the oxidising agent being the oxygen in the atmo

(1) Manufacture of chemical preparations by Ozone. (2) Treatment of oils, fats, and waxes, and similar sub-sphere, the action of which is accelerated by sunlight and

stances by Ozone.

(a) Bleaching.

(b) Deodorising.

(c) Refining.

(d) Technical oxidising.

In addition to these there are other applications which, although oxidation processes, are actually employed in the course of manufacture of goods. These processes include drying of linoleum, fishing nets, waterproof materials, printed matter, varnished or painted articles, &c.,

by moisture, e.g., dew.

Many chemicals have been proposed and used for assisting this natural oxidation, such as potassium bichromate, potassium permanganate, manganese dioxide, bleaching powder, persulphates, perborates, sodium peroxide, hydrogen peroxide, and various organic peroxides. Most of these are open to objection for certain purposes. Thus for the bleaching of food stuffs it is obvious that no poisonous material should be used; in the bleaching of textiles by means of bleaching powder the chlorine liberated tends to weaken the fibres; sodium peroxide is liable

to explode when in contact with organic matter. In addition most of these "per" salts are very expensive.

(a) Bleaching. The use of Ozone overcomes these difficulties with most substances, and in addition the resultant bleach is much more likely to be permanent than that obtained by reduction, since the natural tendency is for the body to become oxidised on exposure to air. Substances which bleach most readily and efficiently with Ozone are

most

Edible fats and oils,
Soap-making materials,
Industrial oils,
Waxes.

ises these also. The use of Ozone is also found to deodorise coconut oils considerably.

(c) Refining.-Refining of various substances is necessary for the purpose of preparation for articles of consumption. By refining is implied the removal of the disagreeable natural flavour or taste which is inherent in some of these substances, which may be said to include practically all the edible fats and oils referred to under "(a) Bleaching."

(d) Technical Oxidising. This term is used to discriminate between the several meanings of the word "oxidising" and the thickening or drying process as applied to the industrial drying oils, such as linseed oil. Whilst this renders them unsuitable for soap making it The first include margarine and nut-butter and various possesses great advantages in the paint and varnish inanimal and vegetable fats, such as tallow, lard, palm oil,dustry, the drying properties of the oils being increased coconut and palm kernel oils, and "stearines," cacao and accelerated, so that there should be considerable scope butter and other so-called chocolate fats-e.g., Borneo for the use of Ozone in the production of quick drying tallow, Illipe fat, Dika fat, &c. paints and varnishes, such as are required by coachThe fact that these are intended for internal consump-builders, shipbuilders, and other trades, and the preparation precludes the use of practically all the usual chemical tion of linseed oil as used in the linoleum and waterproofing bleaching agents, as not only is there, of course, great ob- trades. jection to the use of anything of a poisonous nature for the purpose, but also because some processes, particularly those involving the use of mineral acids, tend to spoil the flavour of the oil. Ozone, however, is free from both of these objections, and, indeed, in some cases rather improves the flavour by the removal of impurities, so that it can be very advantageously used for bleaching.

The same remarks apply to salad oils, olive oils, arachis oils, and monkey nut oil, cotton-seed oil, soya bean oil, turnip seed oil, and rape oil, &c., all of which may be more or less satisfactorily bleached by the use of Ozone. As regards soap-making materials, Ozone is a very useful bleaching agent in this industry, doing all that the ordinary oxidation methods will accomplish, but more quickly and effectively and at less cost. The better qualities of palm oil, for example, can be bleached perfectly at a cost of about 2s. 6d. per ton, while the so-called unbleachable palm oils, such as Congo or Salt Pond, are very considerably improved in colour. Fallow, bone fat, and greases are also very readily bleached by treatment with Ozone. Another method of utilising the bleaching effects of Ozone in the soap works is to ozonise the contents of he pan or kettle during the primary saponification or pasting stage, whereby the saponification process is said

to be accelerated.

Industrial oils-that is oils used for paints and varnishes-readily combine with Ozone on account of the larger amount of unsaturated bodies which oils of this class, such as linseed oil, contain. In addition to being bleached by the oxidation of the colouring matter, which is an advantage in connection with the mixing of light colours in the paint and varnish industry, they further absorb a considerable quantity of Ozone, which should accelerate the subsequent drying of the paint.

Many waxes can readily be bleached with Ozone. Beeswax, which is probably the most important of the waxes, can be much more rapidly bleached by Ozone than by the ordinary method of air bleaching. Other waxes for which the Ozone treatment is suitable are Carnuba, Insect or Chinese, and Japan waxes.

As has already been stated, two or three of these processes will sometimes be effected with a single treatment. For instance, edible oils will be bleached and refined at the same time; fats will be bleached and deodorised; oils may be bleached only or bleached and thickened.

Industrial Ozone Plants.

The method of treatment is almost identical, whether for bleaching, deodorising, refining, or oxidising, and the plant used is practically the same, with only slight modifications to suit particular circumstances. Fig. I shows a diagrammatical arrangement of such a plant which was made to bleach beeswax. The process is very simple, and consists essentially in forcing ozonised air through the substance, which is contained in a suitable pan or vessel. Various conditions are used to suit various substances or objects to be achieved. According to the nature of the substance the concentration or strength of the ozonised air must be varied, also the quantity of air per unit of material, and the time during which it is subjected to

treatment.

The conditions of temperature, &c., have also to be considered, but the process, generally speaking, is in almost all respects identical.

Quite apart from the natural advantages which such a system of treatment has over ordinary chemical processes for such materials as are required for human consumption, this method of bleaching, &c., by Ozone possesses actual commercial value and undoubted merit. In most cases the cost is considerably less, whilst in others the length of time now occupied may be very considerably shortened. In many other cases the results obtained cannot be achieved by any other means.

The plant consists essentially of an electrically driven blower, a refrigerating plant for cooling and drying the air to be ozonised, a battery of Ozone generators, and the vessel in which the material is treated. The blower has a capacity varying with the speed at which it is driven and the resistance of the column of material in the treating vessel.

The air now passes into the cooler of the refrigerating apparatus. This apparatus is worked on the direct expansion system; the temperature of the air_issuing from the refrigerating apparatus is about o° C. The object of this cooling of the air is, firstly, to dry the air by deposition, and, secondly, to cool it, in order to keep the electrodes of the ozonisers cool and thus increase their

(b) Deodorising.-The offensive odour which many substances possess is due in most cases to organic matter in a state of decomposition with which they are always more or less associated. This is best illustrated in the case of sewage greases, fish meal, tallows, bone fats, and such like materials. These substances, if left exposed to the ordinary air, develop nauseous qualities, although one would imagine that the oxidising properties of the atmo-efficiency. sphere would at least stay further development. On the other hand, if treated with Ozone they are at once deodorised by reason of the existing organic impurities being oxidised and the cause of putrefaction destroyed. Such substances as oleine and stearine owe their disagreeable odour to chemical causes, but Ozone completely deodor

|

The air now enters the bank of ozonisers through a series of pipes, which are arranged in order to give an equal volume of air to each ozoniser. The high-tension current is supplied by transformers, whose secondary voltage varies from about 7000 to 9000 volts. This secondary voltage is capable of regulation by means of the

FIG. 1.-DIAGRAMMATIC ARRANGEMENT OF AN OZONE BLEACHING PLANT.

A, Air cleaner; B, Electrically-driven Blower; c, Air Delivery Pipe; D, Air Cooling Machine; K, Electric Motor; E, Cold Air Delivery Pipe; F, Ozone Generators; G, Transformer; H, Valve; 1, Ozone Pipe; J, Ozone Injectors; L, Switchboard.

and amounts approximately to 50 kilowatt hours per