Imágenes de páginas
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors]




[merged small][merged small][merged small][ocr errors][merged small][merged small]




No. 528.-FRIDAY, JANUARY 7, 1870.

NOTES FROM THE LABORATORY | used. On decanting this solution from the little guttaOF A

percha tube, upon the powdered charcoal in the decom

posing jar, instant and rapid disengagement of chlorine - SUGAR REFINERY.

| resulted. It is well known that chlorine is slowly evolved By WILLIAM ARNOT, F.C.S.

from the solution referred to in the cold, more rapidly when heat is applied, and still more rapidly on the ad

dition of alcohol and some other organic substances.* I. Dr. Schiebler's Calcimeter.

Animal charcoal, or bone-black, which produced the inThe almost daily use, for some years, of Dr. Schiebler's stantaneous effect referred to, is a very complex agent. expeditious instrument for the estimation of carbonic acid Its peculiar action as a decolouriser is well known. It in carbonates, and the invariably consistent results ob- was, therefore, a question whether this was an action tained, have made it quite a favourite with the author of analogous to decolouration, or if it was due to the action these notes. Believing the instrument to be far too little of some individual substance present in the char. The known, he would seek to call attention to its value, various constituents were tried, one by one, in every case, especially to those who have the charge of sugar re- without producing the result, unless with the carbon, fineries, where the frequent estimation of calcic carbonate which, when as pure as attainable, produced the very in animal charcoal is a desideratum.

same result as the original powdered char. The char, With a little practice, twelve or fourteen estimations minus the carbon only, had no effect. It was, therefore, may easily be made in an hour; and these, if upon the clear that it was the carbon which had brought about the same finely-powdered sample, will, with ordinary care, be instantaneous decomposition. This carbon exists in a found to agree almost absolutely. The saving of time by very fine state of division. Its action, in this case, must this process over the most expeditious of the ordinary be analogous to that of platinum, in mysteriously detergravimetric methods (which alone are applicable to sub. mining the decomposition of certain substances, as the stances like bone-char) will be found to be very great. carbon itself is in no way acted upon. Further experiStarting, in each case, with the sample in powder, the ments were made, to determine whether this action was difference in time is such as easily to repay the first cost similarly promoted by other forms of carbon. Many of the instrument by a few hours work. As the instru- varieties, from both vegetable and mineral sources, were ment is sold with a normal weight and tables of calculated tried; but in no case was the decomposition of the chro. results, no time is lost in after calculations. The volume mate solution promoted to any appreciable extent by their of carbonic acid, and the temperature indicated by the presence. Charred blood was also tried, and with more instrument, are referred to the tables, where the per- success, though the decomposition was by no means so centage quantity of carbonic acid or calcic carbonate is rapid as in the case of the bone-char. at once found. One great advantage of such an expe

III. PrejudICIAL ACTION OF SULPHITES AND SULPHATES ditious method as this is that there is no temptation to be satisfied with first results, as a few minutes suffice to

IN THE REFINING PROCESS. repeat the process. A general description of the instru

Besides the impurities natural to unrefined cane sugars, ment and process, in English, will be found in the last and which vary in quantity, and to some extent in quality edition of “Fresenius” (Quantitative Part); but a perusal also, according to the care bestowed in the manufacture of the original German instructions will be found profit. and other local circumstances, there are not unfrequently able.

present one or more injurious agents which have been In most freshly-burnt bone-chars, traces of sulphides introduced, not as adulterants, but to counteract some are to be found. These, of course, vitiate the results ob-adverse natural circumstance or action. Among these tained by Dr. Schiebler's instrument to a trilling extent ; agents bisulphite of calcium occupies a prominent but the author has not found, over a wide experience position. In several cane-growing countries, the natives, (unless on one occasion), more than 0:5 per cent of the or colonists, are dependent, in great measure, upon wind evolved gases to be hydric sulphide ; so that, for all power for the performance of certain mechanical operapractical purposes, that may be entirely overlooked.

tions; pressing the juice from the cane is one of these.

The canes being ripe and the wind fair, the planter proII. THE ACTION OF Finely-DivideD CARBON ON Solu- ceeds to cut down his crop; but, before this is well ac

TIONS OF THE CHROMATES IN HYDROCHLORIC Acid. complished, the wind falls; wliat is to be done? To allow On the occasion of finding excess of sulphides in a the cut canes to lie in their natural condition until a sample of bone-char, referred to above, an effort was favourable breeze springs up, may be to submit to a very made to oxidise the sulphur simultaneously with the serious loss of crystallisable sugar by fermentation. evolution of the carbonic acid in the decomposing jar, but To counteract this destructive process, bisulphite of only with indifferent success. In the course of the ex- | calcium, mixed with water to the consistency of ordinary periments, undertaken with that end in view, a solution milk of lime, is sprinkled over the canes from time to of potassic bichromate in strong hydrochloric acid was

Gmelin, Cav. Stoc. Trans., vol. iv., p. 120.

« AnteriorContinuar »