The Behaviour oY Glycerine in Radiators.
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A Clean and Reliable Anti-freezing Mixture
Owners of commercial motors which are fitted with in. ternal-combustion engines will he interested to have some authentic particulars by them in regard to the employment of glycerine for the purpose of reducing the freezing point of water, with which it is miscible in all proportions. It is essential that any anti-freezing mixture should not yield a deposit inside the radiator tubes or members, and, for that reason, especially in the case of commercial motors, where heavy engine loads and high engine speeds are more common than in pleasure-car work, with a resulting greater percentage of evaporation per day, engineers do not favour the introduction of mineral salts, such as chloride of calcium. There is, of course, in addition to the question of possible obstruction, that of corrosion to be considered, whilst no data about an anti-freezing substance can be accepted as complete unless first cost and stability in use are also considered. We proceed, therefore, to deal with these vital points in regard to glycerine.
Absence of Deposit.
Crude glycerine is unsuitable for use in radiators, as it usually contains to per cent. of sodium salts : it has a specific gravity of 1.310 and, in addition to the percentage of salts named, contains nearly to per cent, of water and organic matter. It is necessary to purchase the commercial qeality, which is known as " pale distilled " glycerine, and this con_ tains from 98 to 99.5 per cent, of glycerine, compared with
only So per cent, in the crude quality. The " pale distilled " glycerine has a specific gravity of I.26o, and contains only per cent, of salt and organic matter, with 0.9 per cent. of water. This composition precludes the formation of a .deposit in the tubes, even if the water-contents are boiled down very low, and the absence of any such deposit has been fully proved in practice.
No Corrosion.
It is very important to insure the absence of corroding acid, or any other deleterious agent—such as a catalytic carrier of cxygen which might rust the tubes. Glycerine is free from any such reproaches, and a reliable series of experiments on cast iron, cast steel, brass, copper and vulcanised rubber has shown that the loss of weight, after long immersion in a 20 per cent, solution, and at a temperature. above 200 degrees Fahrenheit, is negligible in each case, and these neutral qualities are clearly most desirable.
First Cost and Stability.
" Pale distilled " glycerine can he bought at about ,(1)o per ton, ex any large soapinaker's works. Convenient packages, for delivery in small lots, are either 56-lb. tins or
Jo-cwt. drums,. and, in view of the inevitable addition to works cost and carriage that is involved by packing in the smaller vessels, we should certainly recommend any omnibus company to buy it in drums. Let us assume that the cost in London is as high as los, per cwt. This price, taking into account the specific gravity of 1.260, approximately corresponds with 8s. per gallon. Our table gives the figures for four typical dilutions, and the accompanying diagram shows the fall of the freezing point according to the percentage of glycerine in aqueous solution. We will assume that 20 per cent, of glycerine is sufficient for all ordinary requirements in this country, i.e., a freezing point of 15 degrees below that of pure water : one gallon of glycerine will yield this dilution in a radiator with a capacity of five gallons.
The next matter for consideration is how often renewal would be necessary. In this connection, it is known to chemists that a solution of glycerine in water, on its being heated to evolve steam, loses a small quantity of the glycerine with the steam, and it has been asserted that the volume of new glycerine required to make up such losses will be a constant source of expense. Sut:h is not the case, as we are acquainted with the details of a carefully-conducted test, in which the 20 per cent. .solution was concentrated to one-fourth of its original bulk, after being maintained at a temperature of 210 degrees Fahrenheit for 19 hours, at the end of which lengthy period of evaporation it was found that the loss of glycerine amounted to only 0.4 per cent. The glycerine itself is, of course, unaffected by any degree of heat which can be applied to it in aqueous solution.
General.
Anybody whouses glycerine should mix it and the water before filling the radiator, or should slowly pour the glycerine into the radiator while the engine is running. In no circumstances should glycerine be put into an empty radiator before the water ; the heavier gravity of the glycerine will then cause it to lodge in the water jackets of the cylinders as circulation begins, and a restriction of free circulation can ensue, whilst exclusive contact of concentrated glycerine with the walls of the cylinders, owing to the non-admixture with water, has been known to allow serious over-heating to occur. With the precautions noted, and it must be admitted that their observance is a matter of no great difficulty, glycerine may be usefully carried, either in a tin ready for use, or in the radiator, upon many a commercial-motor vehicle in the winter months.