898 Beet-root. Crystallization.

surface and the liquid to be boiled is maintained.The steam from the boilers (or the exhaust steamfrom the engines) is admitted to the heating surfaceof the first pan only, at 1c in the apparatus shown;it should have a temperature of about 105° to 110°C. ( = about 5 to 7 lbs. steam); this causes the thinjuice to boil rapidly at about 100° C., giving off, ofcourse, vapour of the same temperature. This coolersteam (which, however, contains nearly the samequantity of heat , sensible and latent together, as anequal weight of steam of higher temperature) passesinto the heating chamber of the second pan, and iscondensed into water, at say 85° C., which runs awaythrough a special arrangement not necessary todescribe. The vapour from the sugar liquor in thesecond pan passes into the steam chest of the third,and being there condensed by the colder liquidcontained in the tubes, creates the partial vacuumrequired in the second pan. The vapour from thethird pan is taken straight to a condenser and vacuumpump, such as are used with an ordinary vacuumpan. Space fails in which to consider scientifically'the action of this valuable apparatus or its detailedconstruction. The thin juice, when it has submittedto a certain amount of concentration in the first pan,is passed on to the second, and then in turn to thethird, where it is brought to about 20° to 25° B.

On leaving the third pan it is heated to nearlyboiling point, and again passed through fresh char-coal filters, from which it proceeds to the vacuumpan to be boiled to grain. This second filtration isalways made through freshly-reburnt char, whichremoves more of the impurities remaining after thefirst filtration. As an example of the purificationeffected, a determination by Rabe may be quoted.A “ thick juice,” containing 47-5 per cent, sugar,2‘8 per cent, organic impurities, and 2'6 per cent,ash before filtration, showed after filtration 2’4 percent, of organic impurities and 2 - 0 per cent, ash;or the char had absorbed 14-3 per cent, of the formerand 23 per cent, of the latter. As the vacuum panand its use is described elsewhere, it needs no specialremarks here, except that owing to the often lowquality of the juice operated on, and its alkalinity,the boiling is sometimes slow and difficult. Mar-guerite has found that the addition of a mineralacid, such as sulphuric or hydrochloric—in qualitysufficient, not only to completely neutralize the freealkalies present, but to convert most of the salts oforganic acids present into sulphates or chlorides—greatly facilitates the boiling, and gives a “greensugar ” more easily and better cured in the centri-fugals. Moreover, he found (and extensive practiceon the large scale quite confirms the laboratoryexperiments) that at the temperature due to thedecreased pressure in the vacuum pan, the liberatedorganic acids exert little or no inverting power onthe sugar. It is worthy of note that though Mar-guerite was the first to publicly advocate the useof strong acids in this way, and to explain the safetyof the process, the thing itself had been done ex-tensively long before in Demerara.

The grained sugar, as it leaves the pan, is treated

differently according as it is intended to makeyellow refining sugar, white crystals, or low-qualityloaf sugar. For details of these various treat-ments the reader is referred to special works.Supposing white crystals are to be made, as is mostcommonly the case in France , the masse cuite isallowed to cool somewhat in a shallow tank forthree or four hours; and is then broken up in anagitator with some syrup, and fed into the centri-fugal machines. When as much of the syrup isspun off as possible, the contents of the machinereceive a dash of water, or of the thick juice inthe state in which it goes to the vacuum pan; thisremoves more of the adhering mother liquor fromthe crystals, which are finally cleansed and driedby blowing steam into the basket of the machine bya suitable arrangement.

The syrup from this first crop of sugar is againboiled in the vacuum pan, but on account of its lowquality, only to “string”— i.e., to such a degree ofconcentration that a few drops placed between thefinger and thumb will draw out to a thread two orthree inches long before breaking. It is then allowedto stand in iron tanks, at a temperature of about40° C., for ten days or a fortnight to crystallize.The grained mass is then dug out, broken up withmore syrup, and spun, when it furnishes a crop ofsecond-running sugar. The syrup is again con-centrated to “string,” and allowed to stand for fiveto eight months in large underground iron tanks orbrick cisterns, when a third crop of sugar is obtained.The syrup from this last constitutes beet molasses,which have hitherto found their way to the distillery,but are now being treated as described further on.

The first crop of sugar being crystallized rapidlyat a comparatively high temperature, consists ofalmost pure sugar crystals, coated more or less withtheir mother liquor, which, being removed as de-scribed, leaves a “sugar” rarely containing morethan one-half per cent, of impurity, includingmoisture. The crystals of the second crop, andstill more those of the third, having formed slowly'in presence of large quantities of salts of the alkalies,always contain a considerable quantity of thosebodies united with the sugar, as explained under“ Compounds of Sugar; ” consequently there isafforded a ready means of distinguishing betweenfirst and second or third running beet sugars, or ofdetecting any considerable fraudulent admixture ofthese latter with the former, by first removing alladhering syrup from the grains of the sugar, bywashing with acidified spirit of about 85 per cent,(say Scheibler’s liquid, No. 1), and then ashinga known weight of the residue with sulphuric acid,as usual. A pure first-running sugar will alwaysgive less than 0'2 per cent, of soluble ash, while athird-running sugar may give as much as 2 to 5per cent.

As examples of the composition of yellow Germanbeet sugars and beet molasses, the following analysesare given. It will of course be understood thatthere is very great variation in different samples,according to their origin, &c. :—

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