26 



CLARKE 



observation and theory ; and so form some conception of the 

 magnitude of our uncertainties. For this purpose I make use 

 of Thomsen's average determinations, and in each case, in a 

 final column, give the percentage difference between his highest 

 and his lowest result. Putting the constant at 13 777 calories, 

 the table of comparison is as follows : 



Compound. 



Heat of Combustion, Thomsen. 



Methane 



Ethane . 



Propane 



Trimethjlmethane 



Tetramethjlmethane.. 



Diisopropjl 



Ethylene 



Propylene 



Isobuty lene 



Isoamylene 



Acetylene 



Ally lene 



Diallyl 



Dipropargyl 



Benzene 



Toluene 



Mesitylene 



Pseudocumene 



Methyl chloride 



Ethyl chloride 



Propyl chloride 



Isobutyl chloride 



Chlorethylene 



Chloropropylene 



Allyl chloride 



Ethylene chloride 



Ethylidene chloride... 



Chloracetol 



Chloroform 



Chlorethylene chloride 

 Tetrachlorethylene . 

 Chlorobenzene 



Methyl bromide 



Ethyl bromide 



Propyl bromide 



Allyl bromide , 



Methyl iodide , 



Ethyl iodide 



Methylamine 



Ethylamine , 



Propylamine , 



Isobutylamine , 



Amylamine 



Dimethvlamine 



H,0 Liquid. 



21 1930 

 370440 

 529210 

 687190 

 8471 10 

 999200 

 333350 

 492740 

 650620 

 807630 

 310050 



467550 

 932820 

 882880 

 787950 

 955680 

 I282310 

 I2815IO 



176950 

 3341 10 

 492380 

 650090 

 298340 

 453370 

 454680 

 296360 

 296410 

 453880 

 107030 

 262480 

 195070 

 763880 



184710 

 341820 

 499290 

 462120 



196080 

 353730 



258320 

 415670 

 575740 

 725360 

 890580 

 420460 



H,0 Gas. 



19T084 



339171 

 487518 



635075 

 784562 

 926259 

 312504 

 461471 

 608928 



755515 

 299627 

 446704 

 880705 

 851611 

 756681 

 913988 

 1219772 

 1218972 



161315 

 308052 



455899 

 6036 1 o 

 282705 

 427312 

 428622 

 275514 

 275564 

 422611 

 101818 

 246422 

 145070 

 737822 



169075 

 315762 

 462809 

 436062 



180445 

 327672 



232262 

 379189 

 528836 

 668033 

 822830 

 383979 



Calculated. 



192878 

 337536 

 482195 

 626854 

 771512 

 916170 

 316871 

 461529 

 606188 

 750847 

 296205 

 440864 

 874839 

 833508 

 764623 

 909282 

 I 198599 

 I 198599 



161879 

 306538 

 451 196 



595855 

 285872 



430531 

 430531 

 275540 

 275540 

 420198 

 99883 

 244541 

 192878 

 733625 



168768 

 313426 

 458085 

 437419 



182545 

 327203 



237653 

 38231 I 

 526971 

 671628 

 816287 

 3823 I I 



Percentage 

 Difference. 



4-0.94 

 —0.49 

 — 1. 10 



— I-3I 

 — 1.69 

 — 1. 10 



+ 1-39 

 -fo.oi 



—0.45 

 —0.62 

 — 1.16 

 —1.32 

 —0.67 

 —2.18 



+ 1-05 

 —0.51 



—1.77 

 — 1.70 



+0.35 

 —0.49 

 — 1.04 

 —1.30 

 + 1.12 

 +0.75 



+0.44 

 -fo.oi 



— O.OI 



-0.58 

 -1.94 

 —0.77 

 — I.I4 

 —0.57 



—0.18 



—0.75 

 —1.03 

 -fo.31 



+I.I6 

 —0.15 



+2.32 

 -fo.82 

 —0.35 

 +0.54 

 —0.80 

 —0.44 



Thomsen's 

 Variation. 



0.99 



I-I3 

 0.84 

 0.38 

 0.17 

 0.28 

 0.49 

 0.40 

 0.38 

 0.40 

 1.09 

 0.08 

 0.28 

 0.55 

 0.53 

 0.79 

 0.04 

 0.16 



0.18 



0.06 

 0.35 



0.24 

 0.70 

 0.22 

 2.16 

 1.77 



0.31 



0.09 

 0.23 



cot 

 0.09 



0.02 

 0.22 



1.72 



0.73 

 0.08 



0.21 



O.II 



0.50 



