METHODS OF INVESTIGATION. 239 
HEATS OF COMBUSTION OF ORGANIC SUBSTANCES (Continued). 
Perthelot Thompson-Stohmann Method. 
Stoh- | Stoh- 
Berthe- ati ert B. Rub- 
lot and] and and | Dani-| “jer, | Gibson. 
Asso- | Tang- | Asso- | lewski. . 
ciates. | bein. | ciates. 
6. Polysaccharids: 
Gly cogeniieds seacaesetes sees!) cco 58 4190.6 
Cellulose ............2.0005 4200 |4185.4] 4146 
LARCH Cai sine: snes utes 4228 4182.5) 4123 }......]...... 4164 
DOXA wg dicks sake ue oe bee 4180. 4/4112.3 
Anvil; jar caas oe Releases vines 4187 .1/4133.5] 4070 
ALCOHOLS. ; 
Ethyl alcohol ................ 7068 
GIY COMM sasccss ad sek ean eects | ddia’e os 4112.4] 4317 
Mannite vsceccisueuides, eulaeeaaa 4001 .2/3997 .8] 3908 |......J...... 3959 
Tm osite: e's ants anestas mn scegierecs eats 3676 .8|3679 .6 
ACIDS 
BCEUGCK 4 2 4. dul ote oo wa teaeue an 3490.4 
PALM iti Cis. sides yas ans Mint oed.ahioiey ana (eens 9352.9] 9226 
DlOATle! esque Wales Bae oa Ae een alas a aems 9429 
Qle le fo nash et anbe din doses ake | we ado 9494.9 
Mal One? 3.0 esi 3.2 ncea deacens. Suet 8 ae 1998.2]...... 1960 
SUCCINIC ee iishs. dx egies aches Sai Ras 3006.2]...... 3019 
WATtATIC wis 5 die caine ahem oo apes siesta oes 1745 
Citric: hee due an oh we oa ese 2477 .9]...... 2397 
parison. Just as the chemical analysis shows the total amounts 
of various substances or classes of substances present, so the heat 
of combustion shows the total amount of potential energy which 
has been stored: up in the feeding-stuff. In both cases the knowl- 
edge thus acquired must be combined with data, secured in an 
entirely different way, as to the availability of these ingredients or 
this energy before we can form a judgment as to the relative values 
to the animal. 
CoMPUTATION OF Heats oF CompustTion.—The heat of com- 
bustion of a mixture of various organic substances, such as are 
contained in ordinary foods and feeding-stuffs, is equal to the sum of 
the heats of combustion of the single ingredients. If the latter are 
known we may obtain the heat of combustion of: the material in 
question either by a direct calorimetric determination or by deter- 
mining chemically the proportions of the several ingredients and 
multiplying the amount of each into its known heat of combustion. 
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