HEATING BY ACETATE OF SODA

Abstract

M. A. ANCELIN, Civil Engineer, describes in La Nature a method he has devised of heating for domestic purposes, travelling, &c., by means of acetate of soda. His objet has been to deyise a method that will possess all the advantages of heating by means of hot water, without any of its inconveniences. For this purpose he sought for a vehicle having a great latent heat of fusion, and aftes several preliminary experiments, he, in September, 1878, took out a patent for heating carriages, &c., by means of the latent heat stored in solid substances previously liquefied by heat. In the course of his experiments, M. Ancelin's attention was called by M. Camille Vincent to the acetate of soda, the very slow cooling of which during manufacture had struck him. M. Ancelin then experimented with this substance, and obtained satisfactory results. The duration of the heat in a warming-pan with acetate of soda he finds to be four times that of a warming-pan with hot water in spite of the great calorific capacity of water. This is due to the enormous quantity of heat which must be applied to the acetate of soda in order to change it from the solid to the liquid state, a heat which it again gives off as it resumes the solid state. As the result of his experiments, M. Ancelin finds that the quantity of useful heat is in fact four times greater in acetate of soda than in water. A railway warming-pan containing ii litres of water, in passing from 8o° C., the mean temperature at which it is put in the carriage, to 40° the temperature below which the heat is no longer perceptible, disengages o calories (11X40). The same pan containing about 50 kilogrammes of acetate, in passing from 80° to 40° disengages 1731 calories instead of 440. Practice is in accord with theory, as may be seen from the curves in Figs. 2 and 3. We see how rapid is the decrease in the temperature of the water warming-pan, while For the acetate pan the curve, at first parallel to that of water, suddenly changes at the point which corresponds to the temperature of crystallisation. The curve then remains almost horizontai, and falls very gently, rendering evident to the eye what takes place inside the pan. We obtain this result at a much less expenditure of heat for the acetate than for water. To raise the pan of water of 11 litres from 10° to 90°, four times, there is required 3520 calories. For the same quantity of acetate only 1987 calories are required, showing a saving of 1500 calories in favour of the acetate. In reality the saving is much greater. In the case of the water-pans raised to 90°, they are only at a maximum ot 80° when put in the carriage, and for four heatings we get only 1760 calorics, or 50 per cent. of the heat stored. In the case of the acetate, there are only 256 calories unutilised, or about 12 per cent, of the quantity stored. M. Ancelin claims for his method that it required almost one-half less expenditure of heat than in the case of the usual warming-pans, especially when we consider that the water requires four separate heatings, and the acetate only one. Long journeys can thus be made by rail, say from Paris to Havre, Lyons, Bordeaux, &c., without having to change the warming-pans, a great saving of labour and of annoyance to passengers. Several companies both in France and in other countries now employ M. Ancelin's method of heating; the French Western Railway Company use it in their carriages from Paris to Havre, and also to Dieppe. In England, M. Ancelin states, the London and North Western Company had, last winter, 3000 of his acetate pans in use, and double that number during the present year.