88 HOW CROPS GROW. 
bicarbonate of soda, Na HO CO. The latter is much less alkaline than 
the former, but both turn cochineal to a carmine color. Again, phos- 
phorie acid may form three distinct salts with soda or with lime, which 
will be noticed in another place. Oxalic acid also yields several kinds 
of salts, as do the other organic acids presently to be described. 
Malic acid, C, H, O,, is the chief sour principle of ap- 
ples, currants, gooseberries, plums, cherries, strawberries, 
and most common fruits. It exists in small quantity in a 
multitude of plants. It is found abundantly in combina- 
tion with potash, in the garden rhubarb, and malate of 
potash may be obtained in crystals by simply evaporating 
the juice of the leafstalks of this plant. It is likewise 
abundant as lime-salt in the nearly ripe berries of the 
mountain ash, and in barberries. Malate of lime also 
occurs in considerable quantity in the leaves of tobacco, 
and is often encountered in the manufacture of maple su- 
gar, separating as a white or gray sandy powder during 
the evaporation of the sap. 
Pure malic acid is only seen in the chemical laboratory, 
and presents white, crystalline masses of an intensely sour 
taste. It is extremely soluble in water. 
Tartaric acid, C, H, O,, is abundant in the grape, from 
‘the juice of which, during fermentation, it is deposited in 
combination with potash as argol. This, 
on purification, yields the cream of tartar, 
(bitartrate of potash,) of commerce. Tar- 
trates of potash or @me exist in small 
quantities in tamarinds, in the unripe ber- Fig. 16. 
ries of the mountain ash, in the berries of the sumach, in 
cucumbers, potatoes, pine-apples, and many other fruits. 
The acid itself may be obtained in large glassy crystals, 
(see Fig. 16,) which are very sour to the taste. 
Citric acid, C, H, O,, exists in the free state in the juice 
of the lemon, anid in unripe tomatoes. It accompanies 
malic acid in the currant, gooseberry, cherry, strawberry, 
and raspberry. It is found in small quantity, united to 
