CAKI50X AND TllK 11 V !>!{()( 'A \i\}( >.\S 347 



There is one known substance among the saturated hydrocarbons 

 composed of 1 atom <>t' carbon and 4 atoms of hydrogen ; this is a com- 



I. For molecular quantities in perfect combustion, the following amounts of heat 

 .iven out (when gaseous carbonic anhydride and liquid water are formed i. according 



to the data of Thomson: (1) for gaseous C ,,11.,,,+., : 52'8 + 158'H/t thousand calories; 

 T C,,H.,, ( : 17 - 7 + 158'l thousand calories; (3) according to Stohniann (1888) for 

 liquid satuated alcohols, C,,H.,,,, +._>() : 1T8 + 156'3/i, and as the latent heat of evaporation 

 = about 8-2-rO'6, in a gaseous state, 20'0+156'9; (4) for monobasic saturated liquid 

 acids, C (( H X ,,,O.., : 95'3 + 154'3/<. and as their latent heat of evaporation is about 5'0 + 1'2/i, 

 in a gaseous form, about ( .)()-f 155/i ; (5) for solid saturated bibasic acids, C/iH.^j - 2 O 4 : 

 25:>-s l.VJT.n, if they are expressed as C,,H., )( C.,,HoOj, then 5r4 + 152'6w; (6) for ben- 

 zene audits liquid homologues (still according to Stohmann) C,,Ho,, 6 : 158'6 + 156'3, 

 and in a gaseous form about 155 + 157; (7) for the gaseous homologues of acetylene, 

 C,,H._,,,-o, (according to Thomsen), 5 + 157/t. It is evident from the preceding figures 

 that the group CH._,, or the substitution of CH 5 for H, on burning gives out from 152 to 

 If.!) thousand calories. This is less than that given out by C + H. 2 , which is 97 + 69 or 

 166 thousand ; the reason of this difference (it would be still greater if charcoal were 

 gaseous) is the amount of heat separated during the formation of CH.v The heat of com- 

 bustion of the following solids (determined by Stohmann) is expressed, not in terms of 

 the molecular weight of the substance, but per unit of weight : C 6 H 1U O 5 , cellulose, 4146 ; 

 starch, 4123; dextrose, C 6 H K ,O G , 3692; cane sugar, C u H.,.>O n , 3866; naphthalene, C 10 H 8 , 

 9621; urea, CN.JtjO, 2465 ; white of eggs, 5579 ; dry rye bread, 4421; wheaten bread, 

 4302 ; tallow, 98(55 ; butter, 9192 ; linseed oil, 9323. 



II. The number of units of heat given out during the complete combustion and 

 cooling of the following ordinary kinds of fuel in their usual state of dryness and purity 

 are : (1) for wood charcoal, anthracite, semi-anthracite, tarry coal and coke, from 7200 

 toS-200; (2) for dry, long naming coals, and the best brown coals, from 6200 to 6800; 

 (3) for perfectly dry wood, 3500 ; hardly dry, 2500 ; (4) perfectly dry peat, best kind, 

 4500 ; compressed and dried, 3000 ; (5) petroleum refuse and similar liquid hydro- 

 carbons, about 11000 ; (6) illuminating gas of the ordinary composition (about 45 vols. 

 H, 40 vols. CH 4 , 5 vols. CO, and 5 vols. N), about 12000 ; (7) generator gas (see next 

 Chap.), containing 2 vols. carbonic anhydride, 30 vols. carbonic oxide, and 68 vols. 

 nitrogen for one part b/j iveight of the whole carbon burnt, 5300, and for one part 

 by weight of the gas, 910, units of heat; and (8) water gas (see next Chap.) containing 

 4 vols. carbonic anhydride, 8 vols. N.,,, 24 vok. carbonic oxide, and 46 vols. H 2 , for one 

 part by weight of the carbon consumed in the generator 10900, and for one part by 

 weight of the gas, 3600, units of heat. In these figures, as in all calorimetric observa- 

 tions, the water produced by the combustion of the fuel is supposed to be liquid. As 

 regards the temperature reached by the fuel, it is important to remark that for solid 

 fuel it is indispensable to admit (to ensure complete combustion) twice the amount of 

 air required, but liquid, pulverised fuel, and especially gaseous fuel, does not require an 



98 of air ; therefore, a kilogram of charcoal, giving 8000 units of heat, requires about 

 24 kilograms of air (3 kilograms of air per 1000 calories) and a kilogram of generator gas 

 requires only 0'77 kilogram of air (0'85 kilo, of air per 1000 calories), 1 kilogram of water 

 gas about 4'5 of air (1'25 kilos, of air per 3000 calories). 



III. As one of the most important and extensive applications of combustible matter 

 is the formation of steam and conversion of it into work, we will take as an example the 

 calculation for a boiler burning prr hour ( = 3600 seconds) 100 kilograms of anthracite, 

 giving out 8000 units of heat, and containing 90 p.c. C, 3 p.c. H, 3 p.c. O, and 4 p.c. of 

 a-li and nitrogen. For the combustion of 100 kilos, of such coal, giving 800 thousand 

 units of heat, about 2400 kilos, (counting double the amount) of air will be required, 

 therefore in the smoke there will be 2500 kilos., and as the specific heat of the products 

 of combustion is about 0'25, so, taking the temperature of the smoke passing from 

 underneath the boiler, < = 200 (higher than the temperature of the air), the smoke will 



carry off 125 thousand units of heat, and 187-5 units of heat per second will be communi- 



