3 1S Mr. Hatchett’s additional Experiments 
some bodies by treatment with nitric acid afford but little, and 
others none of the tanning substance. 
The greatest proportion of this substance was yielded by 
indigo, common resin, and stick lac. 
The quantity obtained from asa foetida and gum ammoniac 
was less. 
Benzoin, balsam of Tolu, balsam of Peru, and dragon’s 
blood, were inferior to the former in this respect, so that the 
developement or rather production of benzoic acid * appeared 
partly to counteract the formation of the tanning substance. 
K ' The expression “ production of benzoic acid ” may appear objectionable, and I 
shall therefore take this opportunity to observe, that I much suspect the present esta- 
blished opinion respecting the balsams and benzoic acid to be erroneous. For the 
balsams are defined as bodies composed of resin and benzoic acid ; consequently the 
latter, when obtained in a separate state, is considered as an original ingredient or educt. 
I am however inclined to a contrary opinion, for I consider the balsams as 
peculiar substances, which, although nearly approaching to the nature of resins, are 
nevertheless different in respect to the original combination of their elementary prin- 
ciples, which combination however is with much facility modified by various causes, 
and especially by a certain increase of temperature, so that a new arrangement of the 
elementary principles takes place, part being formed into resin, and part into benzoic 
acid. 
Many facts appear more or less to support this opinion ; for whether benzoic acid is 
obtained by simple sublimation, or by merely digesting benzoin in boiling water, accord- 
ing to Geoff roy’s method, or by the addition of lime, as recommended by Schee LE,or 
by employing alkalis in a similar manner, nothing positive can be inferred from any 
of these operations to prove that benzoic acid is obtained as an educt, but rather the 
contrary, when we reflect on the affinities which are most likely to prevail under the 
circumstances of the different processes, and on the variable proportions of the benzoic 
acid ; and although benzoic acid has been discovered in the urine of infants, in that 
of many adults, and constantly in that of graminivorous quadrupeds, such as the 
camel, the horse, and the cow, ( Sysieme des Connoissances Chimiques, par Four- 
croy, 4to edit. Tome IV. p. 158 ;) yet all this certainly appears to be in favour of its 
being a chemical product. 
I have observed, when benzoin, balsam of Tolu, and balsam of Peru, were dissolved 
