The malic acid exists ready formed in the sour juice of ripe and unripe apples, and many other fruits, and is obtained as follows: Saturate the juice of apples with potash or soda, and add a proper proportion of acetite of lead dissolved in water; a double decomposition takes place, the malic acid combines with the oxyd of lead and precipitates, being almost insoluble, and the acetite of potash or soda remains in the liquor. The malat of lead being separated by decantation, is washed with cold water, and some dilute sulphuric acid is added; this unites with the lead into an insoluble sulphat, and the malic acid remains free in the liquor. This acid, which is found mixed with citric and tartarous acid in a great number of fruits, is a kind of medium between oxalic and acetous acids being more oxygenated than the former, and less so than the latter. From this circumstance, Mr Hermbstadt calls it _imperfect vinegar_; but it differs likewise from acetous acid, by having rather more charcoal, and less hydrogen, in the composition of its radical. When an acid much diluted has been used in the foregoing process, the liquor contains oxalic as well as malic acid, and probably a little tartarous, these are separated by mixing lime-water with the acids, oxalat, tartarite, and malat of lime are produced; the two former, being insoluble, are precipitated, and the malat of lime remains dissolved; from this the pure malic acid is separated by the acetite of lead, and afterwards by sulphuric acid, as directed above. TABLE _of the Combinations of Citric Acid, with the Salifiable Bases, in the Order of Affinity(A)._ _Bases._ _Neutral Salts._ Barytes Citrat of barytes. Lime lime. Magnesia magnesia. Potash potash. Soda soda. Ammoniac ammoniac. Oxyd of zinc zinc. manganese manganese. iron iron. lead lead. cobalt cobalt. copper copper. arsenic arsenic. mercury mercury. antimony antimony. silver silver. gold gold. platina platina. Argill argill. [Note A: These combinations were unknown to the ancient chemists. The order of affinity of the salifiable bases with this acid was determined by Mr Bergman and by Mr de Breney of the Dijon Academy.--A.] SECT. XXVIII.--_Observations upon Citric Acid, and its Combinations._