Hence the question of the use of alcohol as fuel is becoming a very important one, and will be more so in the future. From the agricultural point of view, it has been urged that the alcohol equivalent to this petrol as fuel could be obtained from potatoes or sugar-beet grown in this country, with much benefit to agriculture and to the country at large. It has been estimated that alcohol equivalent to the 120 million gallons of petrol above-mentioned would be produced from about 5 million tons of potatoes, or from 4 million tons if the alcohol were "carbu-retted "with 20 per cent. of benzol. The average crop of potatoes is at present about 5 1/2 tons per acre, but under the best conditions this yield could be more than doubled, with a decreasing cost of production. An average of 12 tons per acre on 600,000 acres would provide the crop necessary for food on the preseut basis, and the petrol substitute as well. It is urged by some agriculturists that a system could be established here similar to that existing in Germany, whereby a central distillery serves a number of farms in a certain area working on a co-operative basis, each farm devoting a guaranteed minimum acreage to potato-cultivation for supplying the distillery. In short, the organisation would be much on the same lines as with co-operative creameries. In such circumstances, the cost of carriage of the potatoes would be saved; the residual products would be returned to the farm as feeding-stuffs and fertilisers; the production of alcohol would provide a simple method of using an excessive crop of food potatoes; and the farmer would be provided with a cheap fuel for his agricultural machinery. And more than all, the country would not be dependent upon foreign supplies for its liquid fuel.

Obviously such a system as that outlined would mean a considerable modification of present revenue methods of distillery supervision.

Whether we should have the requisite amount of suitable land available for such a purpose, after providing for the great increase in food production now contemplated, is another question. The problem of cost in competition with imported materials such as maize and molasses is a further matter for consideration. Yet another is whether, unless a protective import duty is retained, the home.produced alcohol could always compete in price with possible foreign supplies. Predictions have been made that the tropical countries, when their potential resources are developed, will secure a practical monopoly of the alcohol industry, since they possess three of the cheapest sources of alcohol, namely, sugarcane molasses, palm sap, and starch plants such as cassava and arrowroot.

"Garburetted" alcohol. - For fuel and motor purposes it is often found advantageous to mix a hydrocarbon liquid with the ordinary denatured alcohol. Petrol, benzene (benzol), and petroleum have usually been employed, the mixture being termed "carburetted" alcohol. The proportions vary. In some of the German experiments above referred to it was found that, comparing the efficiency of alcohol alone with that of alcohol carburetted with different proportions of benzol, the best. results in motor power were given by the mixture containing 20 per cent. by weight of benzol. Trials of motors in Paris with French methylated spirit (which contains 10 per cent. of crude methyl alcohol) and the same spirit carburetted with 50 per cent. of a hydrocarbon fuel, showed the carburetted spirit to be superior to the other in the ratio of about 10 to 7, as judged by the consumption.

A number of comparative experiments on the use of carburetted alcohol have also been made in this country. The following may be quoted.1

A four-cylinder Maudslay engine running at 1,000 revolutions per minute was tested with different fuels, with the results given below. Petrol of sp. gr. 0710 was taken as the standard, the results with the other fuels being compared with those given by the petrol reckoned as 100: -

Comparing experiments 3, 4, and 5 with one another, it is seen that the mixture of equal parts methylated spirit and benzol gives the best result, so far as this investigation goes. The sp. gr. of the methylated spirit used was 0815, and of the benzol (two qualities) 0885 and 0875.

1 W. R. Ormandy, J. Gas Lighting, 1913, 124, 580.

During the last few years a number of alcoholic mixtures have been recommended on the Continent as suitable for use instead of petrol. In addition to benzol and petrol, some other substances have been suggested for mixing with the alcohol, namely, acetone, naphthalene, ether, acetylene, and even a small quantity of ammonium perchlorate. Some typical mixtures are the following: -

naphthalene in the proportion of 200 grams per litre.

With most or all of these mixtures a preliminary heating of the carburettor is required, and a reduction of the supply of air, as compared with that necessary for petrol.1

Discussing this question of alcohol-substitutes for petrol, 0. Mohr2 remarks that only the simpler mixtures have proved successful. Equal parts of alcohol and benzol, or alcohol 50, benzol 25, and petrol 25, have given good results; and the second mixture has the advantage of not giving deposits in very cold weather. Naphthalene has proved unsuitable owing to the formation of deposits.

An account of some comparative experiments with different motor fuels recently carried out abroad is given by Donath and Groger.3 The following results are stated to have been obtained per litre of fuel: -

A mixture known as "E. H. A." in France includes ether, like the "natalite" already mentioned. The proportion of ether, however, is only about 10 per cent., instead of 40; and benzol or an alternative to the extent of 25 per cent. is included.

The following thermal and other particulars of the methylated spirit used in this country for burning are given by J. S. S. Brame.1

1 K. Dietrich, Zeitsch. angew. Chem., 1914, 27, 543.

2 Ibid., 558.

3 " Die Treibmittel der Kraftfahrzeuge " (Berlin, 1917).