SUGAR.

79

names a considerable variety of different substances areincluded.

233. Sugars are divided into two classes : those wliichare crystallizable, and those which are uncrystallizable,that is to say, those which, when their solution in wateris evaporated, are obtained in the form of regular-shapedlittle grains, like common cane sugar, and those whichunder these circumstances do not form regular grains,but remain thick viscid liquids, like treacle.

234. Sugar exists in a great many vegetables, but itvery frequently happens that there are so many othersubstances present, that the sweet taste of the sugar isquite hidden. It is only in those plants which containa very large proportion of sugar, or which do not con-tain any strong-tasted substances, that we are able torecognise sugar by its sweet taste. Most ripe fruitscontain a large quantity of sugar ; it is likewise foundabundantly in the sap of a good many trees, from someof which it is procured in such quantities as to beextracted as an article of commerce.

235. The composition of sugar is similar to that ofstarch; the proportions in which its three elements,oxygen, hydrogen, and carbon, are united together arevery nearly the same as the composition of starch. Thevarieties of sugar contain slightly different proportionsof these elements : thus, the composition of cane sugaris not precisely the same as that of sugar obtained frombeet-root, or other plants.

236. Gluten and albumen in many respects are very