PHYSIOLOGY. 235 
90. Malic acid, occurs in apples, (Pyrus malus) ; 
quinces, (Pyrus cydonia) ; strawberries, (lragaria 
wesca), and others. 
21. Oxalic acid. In the wood sorrel, (Oxalis 
acetosella) 5 _herb Robert, (Geranium robertianum) ; 
in rhubarb, (Rheum rvabarbarum), and some others. 
22, Tartaric acid. In sorrel, (Rumex acetosa); 
tamarind, (Tamarindus indica). i 
23. Benzoic acid. In benzoin, (Styrax denzoé) ; 
balsam of Peru, (Myroxylon peruiferum); and bal- 
sam of Tolu, (YVoluitera ba/samum). 
94, Ammonia, or volatile alkali, composed of 
azot and hydrogen, is found in the species of gra- 
mina and mustard, as the white and black mustard, 
(Sinapis alba et nigra); in Sysymbrium nasturtium, &c. 
§ 231. 
Besides the elementary substances, and those com- 
bined by the vital power, vegetables contain some 
of the neutral salts: sulphat of lime, nitrat of mag- 
nesia; the last is found chiefly in the Zea Mays, 
nitrat of potass is found in Borago officinalis, Helian- 
thus annuus, Mesembryanthemum crystallinum, Achil- 
lea millefolium, Fumaria officinalis, &c. Sulphat of soda 
in Vamarix gallica, muriat of soda in many sea-plants. 
in America some plants, it is said, have been detected, 
from which muriat of soda may be obtained. Sulphat 
of potass is found in the ashes of most vegetables. * 
S232 
* Still, however, there is an open field for research in 
Shae : 6 : i 
chemistry. We are partly entirely ignorant of many of 
the 
