ee 
Feb. 8, 1883] 
NATURE 345 
for a vehicle having a great latent heat of fusion, and 
after 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 pre- 
the large form is for 
apartments or beds, the smaller for a lady’s muff. 
Fic. 1.—Warming-pans with acetate of soda for domestic use; 
viously 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 
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REFROIDISSEMENT EN HEURES. 
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Fic. 2.—Curves of cooling of warming-pans with water. 
during manufacture had struck him. M. Ancelin then 
experimented with this substance, and obtained satis- 
factory 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 11 litres of water, in passing from 
80° C.. the mean temperature at which itis put in the 
carriage, to 40° the temperature below which the heat is 
no longer perceptible, disengages 440 calories (11 X 40). 
The same pan containing about 50 kilogrammes of 
acetate, in passing from 80° to 40° disengages 173E 
calories instead of 440. Practice is in accord with theory, 
as may be seen from the curves in Figs. 2and 3. Wesee 
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 
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REFROIDISSEMENT EN HEURES 
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Fic. 3.—Curves of cooling of acetate of soda. 
which corresponds to the temperature of crystallisation. 
The curve then remains almost horizontal, and falls very 
gently, rendering evident to the eye what takes place 
inside the pan. We obtain this result at a much less ex- 
penditure of heat for the acetate than for water. To raise 
the pan of water of 11 litres from 10° to 9o°, 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 un- 
utilised, 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 
