The yields represent the solid crystalline residue; this when purified by recrystallisation gives, probably, about three-quarters of its weight of pure crystals. (In the case of dextrose, &c., the yields represent the weight of syrup.)
These numbers, however, by no means represent the maximum yields obtainable, owing to the comparatively slight solubility of hydrogen bromide in chloroform. The process was conducted in the above manner only for the sake of uniform comparison. The ether method previously described gives much larger yields; for example, 12 grms. of inulin treated with only 60 c.c. of the saturated ether gave 2.5 grms. of substance. For the purpose of obtaining larger yields, other methods are being investigated.
The facts recorded above, taken in conjunction with those given in our previous communications, appear to point definitely to the following general conclusions. First, that the various forms of cellulose contain one or more groups or nuclei identical with that contained in lævulose, and that such groups constitute the main or essential part of the molecule. Secondly, that similar groupings are contained in starches and dextrins, but that the proportion of such groupings represents a relatively small part of the whole structure.
The nature of this grouping is, according to the generally accepted constitution of lævulose, the six-carbon chain with a ketonic group:
But the results might, on the other hand, be considered indicative of the anhydride or 'lacton' grouping, which Tollens suggested for lævulose:
The latter very simply represents the formation of ω-brommethylfurfural from lævulose,[7]
giving