SUGAR. —Analysis and Valuation. 889

They also unite with the sugar, and crystallize outwith it when crystals do at last form. These crystalshave not a constant composition, but contain pro-portions of the “ salt ” and sugar, varying with theproportions of those bodies in solution ; the crystalsare anhydrous, and it is probable that the compoundsin definite molecular proportions, which doubtlessexist, are isomorphous with sugar itself, and conse-quently crystallize out along with it in all propor-tions. The interest of these bodies lies in the factthat their solutions are brought to crystallize withgreat difficulty, and that they persistently maintaina state of supersaturation in presence of even manycrystals of their own composition. For after somuch of the sugar of a vegetable juice has beenremoved by evaporation that the salts left in themother liquors are in proportion to form all orany of the above compounds, the liquor becomestoo sticky to admit of the free crystallization evenof that sugar which is still uncombined with salts,and consequently a double loss occurs to the manu-facturer: first, of the sugar which unites with thesalts to form these compounds; and secondly, ofthat which is retained in solution in the practicallyuncrystallizable syrup so made.

The so-called third running beet sugars, whichoften stand in the crystallizing tanks for six months,nearly always contain large quantities of salts actuallycrystallized out with the sugar, mostly chloride andnitrate of potassium.

The experiments of Sciieibleii and Marsciiallto determine the molasses-forming power of cer-tain salts were made by adding a certain quantityof a given salt to a known excess of pure sugar,together with as much water as would naturallyleave a considerable proportion of sugar undissolvedat the ordinary temperature. The mixtures weremade in tubes, which were then sealed before theblow pipe and heated in the water till “salt”and sugar were both dissolved. The tubes werethen allowed to cool, and stood aside at an eventemperature for many weeks; opened, and thequantity of sugar remaining in solution, in propor-tion to the water , was determined. In some casesmore and in others less was found, than if simplypure water had been used. Those salts giving riseto the first case they called “ molasses-forming," andthe second “ negative molasses-forming,” implyingthat their presence had caused more sugar to crystal-lize than otherwise would have done. But theseexperiments were wrongly conceived; for the ques-tion is not what proportion of the sugar present canyou obtain on the first crystallization, but how muchof the total sugar present can you recover by repeatedconcentration. It is certain pure sugar would givethe best result.

Dry sugar melts at 1(30° C. (357° Fabr.) to a colour-less liquid, which on cooling remains glassy forsome time, and then beoomes crystalline and opaque.At a little above this temperature it is said to beconverted into a mixture of dextrose and Isevulosan,and at about 20.0° C. (392° Fahr.) to lose water andbecome a mixture of glucosan and Isevulosan, and atVOL. II.

210° C. (410° Fahr.) to be converted, with furtherloss of water, into caramel; but the evidence onwhich these statements are made is somewhat in-sufficient as regards the composition of the bodiesformed, though water is lost and mixtures of bodiesmore or less brown are formed.

Analysis and Valuation of Sugar , &c. —Reagentsneeded. —The reagents required for the examinationand analysis of sugars and syrups are:—

A solution of basic lead acetate. — Grind togetherin a mortar 1 lb. sugar of lead and J lb. litharge,with enough water to make the whole pasty. Dis-solve in about 3 pints of boiling water, with con-stant shaking till all the litharge has disappeared.Filter the solution, and preserve in well-closedbottles.

A solution of sulphurous acid in water.

Sodium sulphite in crystals..

Washed alumina —made by pouring a solution ofalum into an excess of a hot solution of washingsoda, and washing the precipitate obtained in a linenbag by pouring boiling water continually through it.It is to be mixed with enough water to. form a thincream.

Purified Animal C/iarcoal—Digest 1 lb. of groundnew animal charcoal in 5 or 6 lbs. strong hydro-chloric acid (the common yellow acid will do), dilutedwith twice its own bulk of water, at a boiling heatfor some time; filter off and wash the residue in s.linen bag with boiling water till the filtrate is nolonger acid; dry and ignite to. full redness in acovered crucible, and immediately bottle the stillwarm char in a number of small well - stoppedbottles. It is essential that it be kept dry.

Pure hydrochloric acid.

Pure concentrated sulphuric acid.

Pure copper sulphate in crystals (this must be pureand free from adherent moisture).

Pure Rochelle salt (sodio-potassic tartrate). Thecommercial article sold as pure is nearly alwaysunfit for the purpose to which this reagent isapplied, and needs to be recrystallized at least oncebefore use.

A solution of caustic soda as pure as can be ob-tained. Commercial caustic soda of good quality,when treated with only so much water as to dissolveabout three-fourths of it, makes a solution so strongthat the bulk of the impurities (sulphates, carbonates,&c.) are not dissolved, and may be filtered off throughclean sand. Dilute, the clear syrupy liquor to a spec,grav. of 114, and preserve for use. The last threereagents are used for the preparation of—

Fehling's sohition for the detection and estimationof glucose. For this purpose dissolve 34-G4 grams,of the copper sulphate in about 200 c.c. of water ina beaker, and pour this into a solution of 173 grams,of the Rochelle salt in 480 c.c. of the soda solutioncontained in a litre flask, shaking after each addi-tion. Make up with water to the mark, and bottleoff in a number of small well-stopped bottles, whichheep in a dark cupboard. Prolonged exposure tolight so. alters the solution that it is decomposed onsimply boiling.

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