In other words, the potash is almost equal in the two ashes, but there is nearly thirteen times more soda in beet ash than in cane sugar ash; lime, magnesia, and oxides of iron and aluminium, are in very small quantities in beet sugar ash.

An analysis of the ash of a Demerara cane sugar growing near the sea-coast, by Dr. Wallace, is as follows:

If sugar be ever adulterated by any of the starches, so clumsy a fraud is readily detected by a microscopical examination, and the use of iodine to the residue obtained by dissolving the sugar in cold water, and then filtering.

§ 69. Full Analysis of Sugar.-The full analysis of a raw sugar consists in :

1. Determination of the water driven off at a heat not exceeding 55° to 60°.

2. An optical estimation before and after inversion.

3. Titration with copper oxide before and after inversion. 4. Estimation of the organic acids by treating with sulphuric acid, and shaking up this acid extract in the tube figured at page 69 with ether, until it has dissolved out all the organic acids. 5. Titration of the organic acids with d. n. soda or potash. 6. Estimation of any insoluble matter, whether organic or inorganic.

7. Estimation of the ash and its constituents.

It may also be necessary to estimate the matters precipitated by basic lead acetate; it would be, however, quite sufficient for commercial, and, indeed, for most purposes, to merely estimate the percentage of cane sugar, fruit sugar (if present), water, and organic matter, or water and ash, as in the following analyses:

TABLE V.-COMPOSITION OF RAW BEET-ROOT SUGARS
OF GOOD QUALITY.

TABLE VI.-SOME ANALYSES BY MR. HALSE OF CONCRETES.

as

The difference between the totals and 100 would be returned "unestimated matters and loss."

The methods of estimating the different kinds of sugar are fully considered in the next section, and it only remains to detail the best methods of taking the ash of a sugar.

There are two methods of taking the ash of sugar.

The one is simply to burn the ash in the ordinary way in a platinum dish heated to redness in a current of air. In the case of all substances like sugar or starch, this method is very tedious, and without doubt there is some loss by volatilisation. Landolt* determined the amount of this volatilisation by a series of careful experiments, and gives the following Table (VII.), which may be used as a guide to the correction of the final weight of the ash.

A method recommended and practised by Scheibler was to moisten the ash with sulphuric acid, whereby the combustion is much hastened, and the bases, being obtained as sulphates, approximate more nearly in weight to that of the organic salts naturally in the sugar, which in the other method are obtained as carbonates. It has also been proposed to precipitate the sugar with acetate of lead, and thus obtain the lead salts of the organic acids. The lead compounds are decomposed in the usual way, and the acids set free titrated by potash. The potash Landolt, H., Journ. Für Praktische Chem., ciii. Also, "Sugar Cane,"

combination approximates somewhat more closely to the actual salts of the sugar.

But the best of those methods which attempt to reconstruct from the ash the original salts, is probably that of Laugier, already described at p. 102. Laugier extracts the organic acids by ether, and then adds them to the ash, and evaporates them down with it. As to raw beet sugar ash, the experiments of Landolt appear to show that simply multiplying the potassic carbonate found by 2, gives the amount of organic salt from which it was derived. His experiment was as follows:-Two pounds of syrup were fully precipitated by lead acetate, then decomposed by SH, and exactly neutralised by potash. The solution was next partly evaporated, passed through animal charcoal, and dried. It gave the reactions of chlorine, and of oxalic, malic, and tartaric acids, with a trace of sulphuric acid. Three separate portions were now carbonised, and the proportion for every one part of organic salt of carbonate of potash wasin experiment 1, 2-04; in experiment 2, 2.05; in experiment 3, 1-98: the mean of the three being 2.08.

§70. Glucose, Dextrose, Dextro-glucose, Grape Sugar, C6H12O6H2O -The rotatory power of glucose is 56°. It is soluble in 100 parts of cold water, and very soluble in boiling water; it is Or if Scheibler's process be followed, the alkaline sulphates may be multiplied by 1.54.

soluble in glycerine, in about two parts of rectified spirit, and two of amylic alcohol; but it is insoluble in ether and in chloroform. Dextrose is widely spread in the vegetable kingdom, but is never found unaccompanied by levulose. Dextrose is artificially obtained by heating carbo-hydrates, such as starch or cane sugar, with acids; in such cases, it is accompanied by dextrine, from which it is difficult to purify it. According to Hoppe-Seyler, indeed, it cannot be obtained pure, save from diabetic urine, and the specific rotation usually given is erroneous. He has separated pure grape sugar, dextrine free, from diabetic urine, and gives its polarisation as 53°5. This, however, agrees very nearly with that given by Tollens, who ascribes to anhydrous dextro-glucose a specific rotation of 53°1, and to the dextrose with its water of crystallisation a specific polarisation of 48° 27.

The best way to obtain dextrose from cane sugar in a pure state is, according to Soxhlet, the following:-3 litres of 90 per. cent. alcohol and 120 cc. of concentrated hydrochloric acid are made to act at 45° C. for two hours on 1 kilo. of cane sugar. After ten days, crystals of dextrose form, when the liquid may be concentrated by distillation, and the crystals which have formed removed. In a few days, the whole of the dextrose will have been deposited as a white powder. The crystals are washed with 90 per. cent. alcohol and with absolute alcohol, and crystallised out of the purest methyl-alcohol. Crystallised grape sugar is in the form of little masses of six-sided tables, which melt at 86°, and lose at 100° their water of crystallisation.

§ 71. Levulose (or Levuglucose) is isomeric with dextrose, but distinguished from it by its action on a ray of polarised light-turning to the left, instead of to the right: -106° at 14°, - 53° at 90°. It is obtained in company with dextrose when sugar is "inverted" by the action of a dilute acid. To isolate levulose the acid must be got rid of; for example, if hydrochloric acid has been used, it is precipitated by silver solution; if sulphuric, by baryta water, &c. The solution of invert sugar must be about 10 per. cent. strength. To every 100 cc. 6 grms. of freshly burnt lime must be added, and the whole shaken. By artificially cooling the solution with ice, a crystalline magma is obtained, and by filtration the more soluble dextrose limecompound can be obtained from the less soluble levulose limecompound. The sugar thus obtained can be freed from lime by carbon dioxide.

Levulose is uncrystallisable, but in has not been found possible to separate it entirely from the crystalline glucose, by crystallising the latter out of it. It presents when pure simply the characters of a colourless syrup.