40 



HEAT. 



ter 140: this number multiplied by 10 

 will give the whole quantity of heat 

 contained in water at 32; namely, 

 1400, which points out the actual zero, 

 at which no heat would remain. 



The theorem of Dr. Irvine for calcu- 

 lating the real zero of bodies is thus 

 stated by Dr. Murray: " The capaci- 

 ties of the solid and liquid being as the 

 whole quantities of caloric they contain, 

 it will follow, that the difference be- 

 tween the numbers which express their 

 capacities, is, to the number which ex- 

 presses the capacity of the liquid, as 

 the difference between the quantity of 

 heat which each contains, measured 

 according to the capacity of the liquid, 

 is to the number of degrees which will 

 express the quantity of caloric it con- 

 tains from zero." The above expression 

 will not, it is suspected, challenge admi- 

 ration on account of its clearness ; what 

 succeeds is less objectionable : " The 

 following general formula, therefore, 

 may be given for the calculation. Mul- 

 tiply the number which expresses the 

 quantity of caloric absorbed when the 

 body passes from the solid to the liquid, 

 or given out when it passes from the 

 liquid to the solid state, by the number 

 denoting the capacity of the liquid. 

 Divide the product by the number which 

 expresses the difference in the capacities 

 of the body in its two forms ; the quo- 

 tient will be the number of degrees of 

 temperature between the freezing point 

 of the liquid, and zero measured ac- 

 cording to the capacity of the liquid." 



Dr. Robison, speaking of Dr. Ir- 

 vine's ingenious method of determining 

 the point of absolute privation of heat, 

 and quoting his own words, says his 

 fundamental proposition was, that " the 

 heat which appeared in mixing vitriolic 

 acid and water is the difference between 

 the sum of the absolute heats of the 

 two ingredients, and the absolute heat 

 of the mixture ; while the heats, which 

 each of them separately required for an 

 equal variation of temperature, had the 

 proportion of their respective absolute 

 heats." Therefore, having discovered by 

 such experiments the difference and the 

 ratio of the absolute heats of the ingre- 

 dients, we can find those absolute heats, 

 and the temperature at which those 

 heats commence, or in which the ingre- 

 dients contain no heat at all. Black's 

 Lectures, by Robison, page 505. 



It was considered that the degrees of 

 temperature are the same in all bodies, 

 although different bodies require differ- 



ent quantities of heat to produce these 

 degrees. So that if the distance of wa- 

 ter at 32 be 1400 from zero, all other 

 bodies at the same temperature will be 

 at the same distance from zero ; the 

 distance of each body being measured 

 by degrees according to its own capacity. 



Many different philosophers have en- 

 gaged in this difficult investigation, and 

 have obtained from various experiments 

 very discordant results. 



Dr. Crawford calculating from the 

 capacities of the constituents of water, 

 and the circumstances attending then* 

 combination, states that the absolute 

 zero of water is 1532 below its freezing 

 point. 



Gadolin measured the capacity of 

 sea- salt and of its solutions, in given 

 quantities of water, and having ob- 

 served the degrees of cold produced by 

 the solutions, he calculated from these, 

 and brought out the zero at 1432 below 

 the freezing of water. The same philo- 

 sopher deduced a variety of numbers 

 from other experiments on the mixture 

 of sulphuric acid and water, and on the 

 mixture of snow and salt ; the lowest of 

 which for the zero was 1510, and the 

 highest 3230. 



The results obtained by Lavoisier and 

 La Place are difficult to reconcile with 

 one another, and with those obtained by 

 other philosophers. From experiments 

 on the mixture of quicklime and water, 

 the apparent zero was 3460 below the 

 freezing point ; experiments on sulphu- 

 ric acid and water brought out the zero 

 at 7294 lower than the freezing point ; 

 and it was made to appear by experi- 

 ments on a mixture of nitric acid and 

 quicklime to be 23,837 above the same 

 point. 



Mr. Dalton deduced different num- 

 bers from different experiments, all of 

 the numbers expressing the distance of 

 the zero in degrees of Fahrenheit's scale 

 below the freezing of water : from the 

 mixture of 5| parts of sulphuric acid with 

 one part of water 6400 ; from a mixture 

 of three parts of lime with one of water 

 4260; from seven parts of nitric acid 

 and one of lime 11,000; from the com- 

 bustion of hydrogen 5400, and from 

 the combustion of oil, wax, and tallow 

 6900. 



MM. Clement and De Sormes state 

 the absolute zero at 448 of Fahr- 

 enheit ; while MM. Dulong and Petit 

 fix it at infinity. It is almost super- 

 fluous to remark, after what has been 

 stated, that the results hitherto obtained 



