Mr. M. Robinson has patented some improvements in the process of making and purifying sugars. He applies to the juice a saturated mixture of alum and lime, in the proportion of two pounds of the mixture to a hundred gallons of the juice. These being intimately mixed, the acid is to be neutralized by the appli cation of milk of lime, in the proportion of three pounds to a hundred gallons. If there be an excess of acid, it will be dis covered by the application of the test paper usually employed by chemists to detect acids, and more milk of lime must be added : and if there be an excess of alkali, it may be discovered by the appli cation of the test-paper used for detecting alkalies, and more juice must be added. When the mixture ceases to affect either the test for acid or alkali, the impurities will he precipitated, and may thus be separated ; and the juice thus purified is to be subjected to the usual mode of cla rification and concentration.
Pure raw sugar is now obtained direct from the sugar-cane, without having undergone any subsequent process of decolorization or refining, prepared by effecting the last stages of the concentra tion of the cane-juice in a vacuum, at a temperature insufficient to produce any chemical changes in its constituent parts. By this improved and scientific process of manufacture, no molasses, or uncrys tallizable sugar is formed, and there is, hence, an increase in the quantity of su gar obtained of 25 per cent. This estab lishes the fact, that molasses is not an educe of the cane, but merely a product of the former operation, from the intense and long continued degree of heat em ployed in the processes. The sugar, thus obtained, is in perfect, pure, transparent, granular crystals, developing the true crystalline form of the sugar, and being entirely free from the least portion of un crystallizable sugar or coloring matter. The newprocess is now in complete and successful operation in eight estates in Demerara. From the results of the first trials, the introduction of the present improved process cannot fail soon to be come general, and the product is much approved in the European market.
Instead of open kettles and pans, high pressure steam, and vacuum pans have been introduced, producing an economy in the manufacture. Different forms of steam apparatus are used in different places—such as that of Derosne, De grand, and Z6lieux.
The process of potting sugar, or free ing it from syrup or treacle, (molasses,) as practised in the West Indies and other countries, consists in allowing it to stand for a considerable period of time in hogs head; casks, or cisterns, having holes bored through their bottoms. The force of gravity causes the syrup or treacle gradually to descend through the sugar, and escape through the holes in the bot tom of the hogsheads.
In order, by the above operation, to expel the syrup or liquid sufficiently to render the sugar fit for market much time is necessarily consumed. Besides, large curing-houses, as they are termed, adapted for the purpose must be erected and maintained. An improvement made, consists in effecting the separation of molasses, by a machine of a peculiar con struction, which accomplishes the same through the agency of centrifugal force.
The objects of boiling and evaporating juice is to separate extraneous matters. the addition of blood and lime have for their object, the one to entangle, the other to neutralize the thick and acid impurities, and ultimately separate them from the syrup. Charcoal or ivory black is used to remove coloring matter. Dr. Scoffern's new process dispenses with the use of lime and blood. It is based on the affinity of oxide of lead for coloring matter, as well as for the melacic and other acids, all of which have to be re moved from the syrup. Dr. S. heats the syrup 280° Fehr., and then mixes it with subacetate of lead; a bulky precipitate of melacitate of lead, formed with syrup more or less contaminated with lead, passes through the filter. This lead is then separated in the form of an insolu ble sulphate by a current of sulphurous acid sent through the syrup. After the removal of the metal has been proved by the test of snlphnretted hydrogen, chalk is added to neutralize the acetic acid, and then the syrup is thus sent to the vacuum pan for granulation.
The latest improvement in the purifi cation of sugar is that of M. Melsens of Belgium. This chemist employs acid sulphites, more especially bi-suiphite of lime, for the double purpose of prevent ing fermentation by the action of the sulphurous acid, and of neutralizing the sulphuric acid as fast as it is formed by means of the lime. The results are, that bi-sulphate of lime can be employed in the extraction of sugar as an antiseptic, preventing the production and action of any ferment—and as a substance greedy of oxygen opposing an alteration which its action on the juice could effect. It also acts as a clarifier, coagulating 212° all albuminous and other coagulable mat ters. It also bleaches all coloring mat ters, and prevents their after formation ; and it is alone capable of neutralizing. any acids which exist or may be formed in the juice. The quantity of sugar which is now lost in the bagasse, in con sequence of the impossibility of washing it out unchanged, can be all collected by being dissolved in water charged with bi sulphate of lime. Both M. relsens's and Dr. Scoffern's processes are liable to ob jections; but, even as they stand, they are large improvements in the manufac ture. In the preparation of beet sugar, bi-sulphate of lime is said to be as valuable as for the cane. In this manufac ture, M. Melsens employs a solution of bi-sulphate of lime, of 10° &mime ; the beet-root pulp is sprinkled over with this solution ; 21 parts of bi-sulphate are suf ficient for 100 parts of beet-root. The saccharine solution marking 7° or 8° Beaume when it comes from the press, remains almost colorless when exposed to the air, and does not ferment. It is then heated, without any further addi tion, up to 100° C. and as soon as it boils, it is run off and filtered ; the limpid juice is then evaporated to 80° Beaume,---_ filtered a second time, concentrated to the required degree, and then set aside to crystallize.