NOTES FROM

SUGAR

THE LABORATORY OF A

REFINERY.

By WILLIAM ARNOT, F.C.S.

I. DR. SCHIEBLER'S CALCIMETER.

THE almost daily use, for some years, of Dr. Schiebler's expeditious instrument for the estimation of carbonic acid | in carbonates, and the invariably consistent results obtained, have made it quite a favourite with the author of these notes. Believing the instrument to be far too little known, he would seek to call attention to its value, especially to those who have the charge of sugar refineries, where the frequent estimation of calcic carbonate in animal charcoal is a desideratum.

With a little practice, twelve or fourteen estimations may easily be made in an hour; and these, if upon the same finely-powdered sample, will, with ordinary care, be found to agree almost absolutely. The saving of time by this process over the most expeditious of the ordinary gravimetric methods (which alone are applicable to substances like bone-char) will be found to be very great. Starting, in each case, with the sample in powder, the difference in time is such as easily to repay the first cost of the instrument by a few hours work. As the instrument is sold with a normal weight and tables of calculated results, no time is lost in after calculations. The volume of carbonic acid, and the temperature indicated by the instrument, are referred to the tables, where the percentage quantity of carbonic acid or calcic carbonate is at once found. One great advantage of such an expeditious method as this is that there is no temptation to be satisfied with first results, as a few minutes suffice to repeat the process. A general description of the instrument and process, in English, will be found in the last edition of "Fresenius" (Quantitative Part); but a perusal of the original German instructions will be found profit

able.

used. On decanting this solution from the little guttapercha tube, upon the powdered charcoal in the decomposing jar, instant and rapid disengagement of chlorine resulted. It is well known that chlorine is slowly evolved from the solution referred to in the cold, more rapidly when heat is applied, and still more rapidly on the addition of alcohol and some other organic substances.* Animal charcoal, or bone-black, which produced the instantaneous effect referred to, is a very complex agent. Its peculiar action as a decolouriser is well known. It was, therefore, a question whether this was an action analogous to decolouration, or if it was due to the action of some individual substance present in the char. The various constituents were tried, one by one, in every case, without producing the result, unless with the carbon, which, when as pure as attainable, produced the very same result as the original powdered char. The char, minus the carbon only, had no effect. It was, therefore, clear that it was the carbon which had brought about the instantaneous decomposition. This carbon exists in a very fine state of division. Its action, in this case, must be analogous to that of platinum, in mysteriously determining the decomposition of certain substances, as the carbon itself is in no way acted upon. Further experiments were made, to determine whether this action was similarly promoted by other forms of carbon. Many varieties, from both vegetable and mineral sources, were tried; but in no case was the decomposition of the chromate solution promoted to any appreciable extent by their presence. Charred blood was also tried, and with more success, though the decomposition was by no means so rapid as in the case of the bone-char. III. PREJUDICIAL ACTION OF SULPHITES AND SULPHATES

IN THE REFINING PROCESS.

BESIDES the impurities natural to unrefined cane sugars, and which vary in quantity, and to some extent in quality also, according to the care bestowed in the manufacture and other local circumstances, there are not unfrequently present one or more injurious agents which have been introduced, not as adulterants, but to counteract some adverse natural circumstance or action. Among these agents bisulphite of calcium occupies a prominent position. In several cane-growing countries, the natives, or colonists, are dependent, in great measure, upon wind power for the performance of certain mechanical operations; pressing the juice from the cane is one of these. The canes being ripe and the wind fair, the planter proceeds to cut down his crop; but, before this is well accomplished, the wind falls; what is to be done? To allow the cut canes to lie in their natural condition until a favourable breeze springs up, may be to submit to a very serious loss of crystallisable sugar by fermentation. To counteract this destructive process, bisulphite of calcium, mixed with water to the consistency of ordinary milk of lime, is sprinkled over the canes from time to * Gmelin, Cav. Stoc. Trans., vol. iv., p. 120.