SO2 (sulphur dioxide) + H2O (water at low temperature)-->H2SO3 (sulphurous acid). Another thing of very great importance is the cooling of the gases to condense any water that may be present so that no hot gas will reach the juice to be treated or combine with water in the pipes. The equation represented when high temperatures are used is as follows: SO2 (sulphur dioxide) + H2O (water) + O (high temperature)-->H2SO4 (sulphuric acid). This last-named acid is very corrosive and a powerful investing agent. It therefore has the property of rapidly destroying sucrose, especially at a high temperature. In the burning of sulphur it is well that as thorough a combination as possible be obtained, else there will be a loss of sulphur, which will deposit in the tubes and choke them, and more time will be required for the process. The fumes from a well-regulated sulphur furnace should contain from 15 to 16 per cent sulphurous acid. The theoretical percentage obtainable is about 21 per cent of the acid. Carbon dioxide.--In recent years carbon dioxide gas has found a very useful application in the cane-sugar factories, where a good grade of plantation sugar is desired. Java factories have been the foremost in elaborating a system, through their eminent technologists, so that today one may find the bulk of the sugars they turn out from certain factories of a very satisfactory grade and color. The method they use requires a great deal of skill and attention in order to yield results that are satisfactory. It is patterned after the process used in beet-sugar factories, with some distinct modifications, which make it applicable to a juice containing glucose, as is always the case with cane juices. The object of applying any clarifying material is to effect a rise in purity, and it is especially desirable to remove, in all cases, the substance added, since this itself would tend to act as an impurity and thus give a lower coefficient, if not properly removed. The lime, which has been added previously, may be partly removed, as the original precipitate formed, and any free lime or compound which may be easily decomposed will combine with carbon dioxide, forming calcium carbonate or limestone, which is quite insoluble and may be very easily filtered off. Ca(OH)2 (calcium hydroxide) + CO2-->CaCO3 (calcium carbonate) + H2O (water). Whether single or double carbonation is used, the same general methods are employed, and results are expressed by the same chemical equation. As stated before, the carbon dioxide may be recovered from the kilns during the burning of lime, as is commonly done in the beet-sugar industry, or it may be purchased in the form of liquid CO2 contained in heavy iron containers. It is also feasible to use flue gases for this purpose, where a good combustion is obtained, and after they have been properly treated.