The name hesperidin had also been applied to yellow crystals extracted from the shaddock, Citrus decumana L., the dried flowers of which afford about 2 per cent. of that substance. It is, as shown in 1879 by E. Hoffmann, quite different from hesperidin as described above; he calls it Naringin and assigns to it the formula C₂₃H₂₆O₁₂+4OH₂. Naringin is readily soluble in hot water or in alcohol, not in ether or chloroform. Its solutions turn brown-red on addition of ferric chloride.
Lemon juice, some of the characters of which have been already noticed, is an important article in a dietetic point of view, being largely consumed on shipboard for the prevention of scurvy. In addition to citric acid it contains 3 to 4 per cent. of gum and sugar, and 2·28 per cent. of inorganic salts, of which according to Stoddart only a minute proportion is potash. Cossa[466] on the other hand, who has recently studied the products of the lemon tree with much care, has found that the ash of dried lemon juice contains 54 per cent. of potash, besides 15 per cent. of phosphoric acid.
Stoddart has pointed out the remarkable tendency of citric acid to undergo decomposition,[467] and has proved that in lemons kept from February to July this acid generally decreases in quantity, at first slowly, but afterwards rapidly, until at the end of the period it entirely ceases to exist, having been all split up into glucose and carbonic acid. At the same time the sp. gr. of the juice was found to have undergone but slight diminution:—thus it was 1·044 in February, 1·041 in May, and 1·027 in July, and the fruit had hardly altered in appearance. Lemon juice may with some precautions be kept unimpaired for months or even years. Yet it is capable of undergoing fermentation by reason of the sugar, gum, and albuminoid matters which it contains.
Commerce—Lemons are chiefly imported from Sicily, to a smaller extent from the Riviera of Genoa and from Spain. From the published statistics of trade, in which lemons are classed together with oranges under one head, it appears that these fruits are being imported in increasing quantities. The value of the shipments to the United Kingdom in 1872 (largely exceeding those of any previous year) was £1,154,270. Of this sum, £986,796 represents the value of the oranges and lemons imported from Spain, Portugal, the Canary Islands and Azores; £155,330 the shipments of the same fruit from Italy; and £3,825 those from Malta.
Of concentrated lemon juice there were exported in 1877 from Messina 1,631,332 kilogrammes, valued at 2,446,996 lire. The value of concentrated lime juice exported in 1874 from Montserrat was £3,390. From Dominica, 11,285 gallons, value £1,825, were shipped in 1875.
Uses—Lemon peel is used in medicine solely as a flavouring ingredient. Freshly prepared lemon juice is often administered with an alkaline bicarbonate in the form of an effervescing draught, or in a free state.
Concentrated lemon juice is imported for the purpose of making citric acid; it is derived not only from the lemon, but also, to a smaller extent, from the lime and bergamot. Lime juice of the West Indies is chiefly used as a beverage; small quantities of it are also exported for the manufacture of citric acid. The culture of Citrus Limetta Risso, the lime, was introduced in Montserrat in 1852.
OLEUM LIMONIS.
Oleum Limonum; Essential Oil or Essence of Lemon; F. Essence de Citron; G. Citronenöl.
Botanical Origin—Citrus Limonum Risso ([see p. 114]).