OF ANIMALS FED AND SLAUGHTERED AS HUMAN FOOD. 
871 
the actual analytical results are given ; in the middle division the same calculated to 
exactly 100 ; and in the lower division the results are calculated to 100 excluding sand 
and charcoal—that is, showing the composition of what may be called the pure ash. 
In E. Wolff’s two volumes—‘ Aschen-Analysen he excludes carbonic acid, as 
well as sand and charcoal, in calculating the composition of what he terms “ Rein- 
asche.” This exclusion could hardly be avoided in arranging for comparison the 
recorded results of various analysts, in many of which carbonic acid was not included ; 
and from the point of view of the chemical statistics only, of crops and other products, 
it is of little consequence. As, however, in many cases, the amount of carbonic acid 
represents, more or less exactly according to circumstances, the quantity of base 
which has been in combination with organic acids, its amount, and the differences 
in its amount, in different descriptions of ash, are indications of considerable interest. 
Obviously, in the case of ashes of such heterogeneous mixtures as those now in 
question, the record is of less importance from this point of view ; whilst in some of 
the animal matters carbonates doubtless exist as such. But, as in other cases it is 
important to include the carbonic acid among the constituents of the pure ash, it is 
included here also for the sake of uniformity of plan. 
It is freely admitted that results relating to carbonic acid require very careful con¬ 
sideration, if misinterpretation is to be avoided. Not that the determination of the 
amount of it actually existing in an ash is a matter of difficulty in experienced hands ; 
but, according to the character of the ash, and to the conditions of the incineration, 
more or less of the carbonates may have been converted into more fixed salts, or the 
carbonic acid may be expelled and the ash causticised. 
It is in fact very difficult, if not impossible, with some descriptions of ash, such for 
example as contain much silica, or phosphates with less than three of fixed base, so to 
conduct the incineration as to retain what may be termed the normal amount of car¬ 
bonic acid. Indeed, after an ash has been kept for some time, and has acquired water, 
and perhaps regained carbonic acid, it is in some cases extremely difficult finally to 
heat it before weighing out for analysis, so as to ensure, on the one hand the expulsion 
of all water, and on the other the retention of the normal amount of carbonic acid. 
These points have been very fully investigated in connexion with the analyses of 
about 700 ashes, of various products, of known history, prepared at Rothamsted. 
In the ashes of the mixed animal matters the amount of carbonic acid is in all cases 
small; but the differences in the amounts obtained according to the methods of pre¬ 
paration for analysis well illustrate the difficulties involved. Thus, in five of the 
carcass ashes, and in eight of the entire animal ashes, carbonic acid was determined :— 
1, in the ash some time after preparation and without re-ignition (but calculated on 
re-ignited ash); 2, after re-ignition preparatory to weighing out for the determination 
of other constituents; 3, after treatment with ammonium carbonate and exposure to 
very low red heat. The average amount in the five carcass ashes was—determined in 
the not re-ignited ash 2 - 59, in the re-ignited ash 0'87, and in the ash treated with 
5 T 2 
