iSyi,] Heat. 425 



that he has obtained what he calls chloroform snow and iodethyl snow, by 

 directing a rapid and moist current of air upon these fluids contained in 

 shallow basins. As regards the real nature of these solid substances, his 

 experiments are not yet quite finished. 



The freezing-point of mixtures of glycerine and water has been examined 

 by Mr. C. Bullock. The glycerine used was common, sp. gr. = 1*250 ; the 

 quantity of water, in all experiments, 1 gallon. Temperatures Fahr., with 

 £ pint, fuses at 30 , 1 pint at 24 , i£ pints at 18 , 2 pints at io°, 3 pints 

 remain fluid at 3 . These determinations are of considerable value, as mix- 

 tures of glycerine and water are frequently used in cases where a mobile liquid 

 is required at temperatures where water would be solid, — e.g., in wet gas 

 meters, ice machines, &c. 



An ammonia engine has been designed by Mr. Emile Lamm, in which am- 

 moniacal gas is used as a substitute for steam or air. Ammonia, at the 

 temperature of our atmosphere, is a permanent gas of well-known pungent 

 odour. Its density is 596 ; air being 1000. It may be liquefied by great 

 pressure, and in the fluid state its density, compared with water, is 76, or 

 about one-quarter lighter than that liquid. Its vapour, at 6o° Fahrenheit, 

 gives a pressure of 100 pounds to the square inch, while water, to give an 

 equivalent pressure, must be heated to 325 Fahrenheit. The volume of am- 

 moniacal gas under the above-named pressure is 983 times greater than the 

 space occupied by its liquid, while steam, under identical pressure, occupies a 

 space only 303 times greater than water. If, therefore, by the application of 

 equal quantities of heat to the specific heat of equal weights of steam and 

 ammonia, such great difference in their relative volume is produced, it is evi- 

 dent that the cost of ammonia, as a motive power, would be one-third that of 

 steam. This immense volume of the gas, compared to other gas or vapours, 

 shows a decided exception to the law of Mariotte, relating to the expansion of 

 gases, greatly in favour of ammonia as a motive power. The latent heat of 

 ammoniacal gas is 880, that of steam being ggo. Ammonia is a powerful 

 alkali. Its action upon most of the metals is nil ; still, strange enough, it 

 acts slowly upon one of the metals of the second class — i. e., copper. Upon 

 metallic iron, which is a metal of the third class, its action is absolutely nil ; 

 but it readily dissolves carbonated oxide. Ammoniacal gas is absorbed by 

 water with avidity, one volume of water at 70 Fahrenheit absorbing 500 

 volumes of the gas. The water becomes specifically lighter, whilst its volume 

 is augmented about one-third. As the absorption of the gas goes on, the 

 water becomes heated, and the latent heat of the gas reappears as sensible 

 heat. It is in this property that water possesses of absorbing so large an 

 amount of the gas, and of becoming heated while absorbing it, that the prac- 

 ticability of using ammoniacal gas as a motive power rests, for it must be well 

 borne in mind that the only agency for producing motive power is heat. It 

 matters very little that liquefied ammoniacal gas boils at 40 below zero — 72 

 below the freezing-point ; it requires as much heat comparatively as water 

 itself, for its complete and rapid evaporation, when acting as a motive power 

 in an ordinary engine. But ammoniacal gas possesses the remarkable pro- 

 perty, from its affinity for water, of being able at any time after its condensation 

 into a liquid to reproduce, at a distance from the receiver where it was con- 

 densed, a force equal to the heat which was necessary for its condensation. 

 This reproduction is owing to the fact that the latent heat of the gas appears 

 anew in water of re-absorption, and is re-transferred to the liquefied gas. The 

 re-transfer of the heat to the liquefied gas takes place, through metallic tubes 

 of which the reservoir is composed, from the water of re-absorption which 

 surrounds them, and is similar in its operation to the action of fire in the 

 furnace of a steam boiler. An engine driven by ammonia instead of steam 

 has actually been in use for some time in America, for the purpose of driving 

 street cars. In the last trip of seven miles made by a street car driven by 

 ammonia, the engine used on the car was equal to two-horse power ; the am- 

 monia expended during the trip amounted to ri6 cubic feet. The latent heat 

 vol. viii. (o.s.)— vol. 1. (n.s.) 3 1 



