The quantity of sugar in a sample of cane-juice may be approximately ascertained from its density. This is observed by a hydrometer. As the indications of this instrument refer to the proportion of solid matters in the liquid, without reference to their character, they need correction for the solids other than sugar. The following table will be found useful for this purpose : The Mineral Matters.The quantity of mineral salts in the juice of canes best fitted for sugar making is about 0.29 per cent. of the liquid. They are found in greater proportiou in the head than in other parts of the cane. The nature of the soil has a marked influence, and to it the variations in the figures must be referred. The principal mineral matters are potash, soda, lime, and iron, as oxides, carbonates, chlorides, sulphates, hiphosphates, and silicates ; with these, are salts of alumina and magnesia. The annexed analysis of cane ash shows the average proportions of tbe most important : Potash aud soda .. 18.83 per cent.
Lime .. 8.31 Oxide of iron .. 1.99 Silica .. 11.48 Alumina, magnesia, aud acids in combination with the bases .. 59.36 The Organic Matters.The vegetable (organic) matters contained in cane-juice (excluding the sugar itself) may be divided into 3 groups :(1) Substances which communicate a milkiness to the liquid, and aro with difficulty precipitated from its upper layers on standing, hilt may be easily and almost completely separated hy filtration, juice thus filtered having the property of keeping nearly 24 hours without undergoing fermentation ; (2) albuminous material capable of coag,ulation by boiling, or even by heating to 80° (176° F.), and precipitable by strong acids without being re
soluble in excess ; (3) albuminous bodies not coagulated by heat, hut precipitable by alcohol and by lead acetate, and soluble in alkalies and acids (even tannic a.cid). Juice which has been heated and filtered may be kept perfectly fresh for some few hours, at a temperature of 30' (86° F.). At the end of this period, a thin pellicle is seen, and on the next day, a slight cream covers its surface, and the colour changes; but it hi only at the eud of the second day that fermentation positively shows itself. It thus appears that it is sufficient to rapidly heat the newly-extracted juice, and filter it immediately, in order to have a limpid liquid, which can be kept for a considerable time without very great alteration. Further, these substances develop acidity in the juice, and are one of the principal causes of the formation of uncrystallizable sugar. When they are eliminated, acidity is only feebly increased by the action of heat.