892 SUGAR.— Valuation from Analysis.
with the sulphuric acid, and return to the muffle.Let it remain at a low heat till the ash is quitewhite, then raise the heat to full redness for tenminutes, withdraw, cool, and weigh. From theweight of sulphates so obtained deduct one-tenth, *and call the balance “ ash.”
On adding together the sugar, glucose, ash, andwater found as above, it will be found that the totalis something short of 100—usually to the extent ofone and a half times to twice the weight of the ash ;this difference is called “unknown” or “organicmatter.” As examples of such results, we may takethe following analyses of low cane and beet sugars:—
Sugar,.
Beet Sugar.
Sugar,.
Cane Sugar
.... 88-2
_
_ 5-85
Ash,.._
Water,.
Ash,.
•90
.... 4-26
Water,..
Unknown,..
.... 3-96
Unknown, ..
. 1-07
100-00
100-00
In the absence of a polariscope, or in cases wherethe quantity of sugar at command is too small toestimate by the use ■ of that instrument, it may benecessary to determine the cane sugar present as wellas the glucose by the use of Fehling’s solution.For this purpose take a quantity of the materialwhich contains about 10 grams, of sugar, clarifyit as for polarization, taking care to leave no lead insolution; make it up to 1000 c.c. Estimate theglucose in one portion diluted with its own bulk ofwater; then take 50 c.c., add 5 c.c. hydrochloricacid, heat to 70° C. for five minutes, cool, nearlyneutralize with sodium carbonate, make up to 100c.c., and again determine the glucose. The differencein the glucose found in the two experiments is theglucose formed by the inversion of the cane sugarpresent. Each 0'05 gram, glucose so found — 00475gram, cane sugar originally present in the portionused to decompose the 10 c.c. Feiiling’s solution.Of course material equal to about 1 gram, sugarcan be made up to 100 c.e., as above, instead of 10to 1000; the latter is recommended, to diminishthe influence of errors of sampling. Some chemistsestimate glucose gravimetrically instead of volu-metrically— i.e., they weigh the cuprous oxide pre-cipitated from an excess of Fehling’s solution by aknown portion of the material under examination,after converting it into cupric oxide by ignition,and from this weight calculate the quantity of glu-cose ; 397'5 parts of oxide obtained correspond to180 parts of glucose, or 171 parts of cane, approxi-mately ; but the quantity of copper salt reduced bya given weight of glucose varies so much with thedilution, the alkalinity, the excess of copper saltpresent, and with the speed of the operations, thatthe method is only really applicable to the deter-mination of comparatively small quantities.
Valuation of Sugars from the Analysis .—Raw or
* A continental practice, which is wildly supposed to re-duce the sulphated ash to the same weight as the plaincarbonated ash. As the operations of the trade are based onthe weight of ash so found, it is necessary to adhere to thecustom.
refined sugars fit for direct consumption are valuedin an arbitrary manner, according to their appear-ance, colour, grain, &c., quite irrespective of theircomposition. Refiners value “ sugars ” mainlyaccording to their estimate of the probable yield ofpure dry sugar when submitted to refining. Formarket purposes the so-called French system isadopted. From the sugar found by the polariscopeis deducted five times the weight of the ash, becauseit is assumed that the saline matters, represented by1 part of ash, render 5 parts of sugar uncrystalliz-able; and from the remainder is deducted theweight of the glucose, because it is assumed thatthat body prevents the crystallization of its ownweight of sugar, and the final result is taken as the“ refining value ” ( rendement ) of the given raw sugar.
A beet sugar giving in this way a refining value of88 per cent, is taken as a standard of value, and othersugars are sold at so much a degree more or less.The above method rests on so many assumptions,which are all more or less demonstrably false, thatno one can seriously suppose that the results re-present anything more than a very rough approxi-mation to the truth.
Scheibler, by improving the working details ofa method proposed by Payen, determines thequantity of sugar already crystallised in a sample ofraw; and assuming, as is generally true, that allthe sugar is crystallized that can be—in other words,that any sugar which is still in solution in the syrupadhering to the grains is associated with so muchother matter that it is not recoverable—takes thequantity so found as the true refining value, becauseit is presumable that what has been crystallizedonce may be crystallized again. The method isbased on the fact that alcohol already saturatedwith sugar is capable of dissolving molasses, thoughincapable of taking up more sugar. He preparesthree liquors by saturating alcohol of 85 per cent.(No. 1), 92 per cent. (No. 2), and 96 per cent. (No.3) respectively with sugar, by long-continued shak-ing with the finely-powdered material at ordinarytemperatures. The 85 per cent, spirit has about 5per cent, of ordinary acetic acid added to it beforesaturation.
These liquors are preserved in bottles, coated onthe inside with a crust of sugar; or, as the writerfinds better, in large bottles quite filled with ordi-nary loaf sugar, free from dust, broken as it is forthe table. This is to maintain a constant state ofsaturation, whatever the changes of temperature maybe; but spirit which is nearly saturated with sugardissolves the rest required with such slowness, thatthe maintenance of a nearly constant temperatureis of great importance.
He weighs off the normal weight of sugar requiredfor the polariscope in use; puts it into a tube likea test-tube, of about 8 inches by three-quarters,with a bit of quill tube fused into the bottom, andhaving a filter of thick felt or cotton-wool at thepoint of contraction. The narrow tube is attachedby india-rubber, furnished with a compression cock,to a bottle in which a partial vacuum cau be created.