h ~ 



L. MECHANICS AND EXGINEEEING. 47 



to 400 C. liquid carbonic acid could be distilled irom these 

 salts under a pressure of 50 to 60 atmospheres. 



This fact he considers of great importance, as carbonic 

 acid under high pressure (or, as Beins calls it, " Carbole- 

 ura") is physically a very remarkable body, which may be 

 easily obtained in large quantities. The study of the rela- 

 tions of bodies submitted to high pressure is only in its in- 

 fancy, and to pursue it a simple apparatus for compression 

 is all-important. For pressures of less than 50 or 60 atmos- 

 pheres it is of course not necessary to raise the temperature 

 to 300 and 400 C. With a saturated solution of bicarbo- 

 nate of soda, heated to boiling point in a bath of concentrat- 

 ed common salt, carbonic acid of three to five atmospheres 

 is obtained, and the pressure increases regularly with the 

 temperature. 



Carbonic acid at a high pressure, or carboleum, supplies 

 excellent motive power for small and great industries. This 

 was remarked by Faraday, who discovered liquid carbonic 

 acid, and, since, by Thilorier and others ; but unfortunately 

 the law of the preservation of the energy, indispensable in 

 such cases, was not known. A liter of carboleum at 15 C, 

 and with a pressure of 50 atmospheres, weighs approximately 

 0.8 kilos., and will produce 400 liters of carbonic acid at the 

 ordinary pressure. The power required to produce compres- 

 sion to the extent of 50 atmospheres is equal to about 17,000 

 kilogrammeters. This gives 270,000 kilogrammeters per 

 hour, and per horse-power, for 16 liters of carboleum at 50 

 atmospheres, and 15 C. 



It is only when a carboleum engine works with large in- 

 tervals between that the heat of evaporation can be carried 

 to the sides without heating artificially. In the majority of 

 cases the carboleum must be evaporated by the artificial 

 heating of small quantities at a time. The heat required 

 per horse-power per hour, as already given, namely, 270,000 

 kilogrammeters, is equal at least to 640 calorics (0.1 kil. of 

 coal). 



Large carboleum engines should be worked with regenera- 

 tion. They should have a depot of salt of soda and carbole- 

 um, so arranged that the decomposed bicarbonate shall be 

 regenerated by the carbonic acid which has worked the en- 

 gine. Such a machine transforms very advantageously into 



