November, 1930
IND UXTRIAL AND ENGINEERING CHEMISTRY
content, which finally exits as bottoms from settling tank
KO. 2. The capacity rating of this pilot plant was about onesixth that required for a full commercial plant to handle the waste sulfite liquor resulting from 120 tons pulp production per day. It was operated continuously for 4 months and complete records were kept on the whole run which gave a close audit on the gallonage and content in lime, sulfur, and organic matter of input against similar items for the end products. This involved detailed records on gallonage and weights, careful sampling, and complete analyses on all stages of the process. Experimental cooking tests on wood were than conducted using a cooking acid made entirely from the inorganic product (calcium sulfite), and burning tests were made on the organic product to determine its suitability as a boiler fuelboth with fully satisfactory results. From this pilot plant run it was concluded (1) that the process is commercially feasible to install and operate; (2) the values under Wisconsin conditions of the recovered products for making fresh cooking acid and for a boiler fuel will carry the process and show some net profit; (3) that the tail-liquor effluent from the process has much less oxygen demand than the untreated liquors and probably less toxicity. Prior to making a full commercial installation of the process it was decided to investigate the recovered organic product for more profitable uses than as a boiler fuel and to study the tail-liquor effluent as regards recovery of additional commercial products-all with a view to rounding out the project. This research program is now under way. Effect of T r e a t m e n t on B. 0. D.
The oxygen demand of waste sulfite liquor is commonly regarded as an index of its stream-polluting influence and the tendency of such liquors to deplete the oxygen supply is probably the major action involved, but the toxicity of its constituents may also be a factor. To determine what effect this processing had on the oxygen demand, an investigation was made on the demand of the tail-liquor effluent of the process in comparison with the demand of the raw or untreated liquor. The Rideal-Stewart method as prescribed by the Wisconsin State Board of Health for biochemical oxygen demand was used, but modified by omitting the preliminary permanganate-oxalic acid treatment and by using different dilution factors for the immediate and the long-time demands. The permanganate treatment did not seem necessary in getting the comparative demand of the treated and untreated liquors and the tests in which this preliminary treatment was used gave erratic results. There is a possibility of error on adding such a compound as potassium permanganate to a system in which dissolved oxygen is being determined and errors will also result from any excess of oxalic acid in the alkaline or the subsequent acid stage of the test. Since it is practically impossible to know the exact amount of such excess, it is not possible to correct for it. Authority for this omission was found and it seemed permissible unless there might be some oxidizable matter in the sample which, while it would not oxidize by the dissolved oxygen, might carry through to the final acid stage of the test and react with iodine, thereby being reflected in a high oxygen demand. Careful tests were made to determine any error from this source, but no evidence of such error could be found. Since accurate results for the 1 to 5 day demand could not be obtained when using the standard 4000 dilution, especially on samples with as low a demand as the tail liquors
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show, an 800 dilution was adopted for the 1 to 5 day demand and higher dilution for the long-time demand. The B. 0. D. tests led t o the conclusion that the tailliquor effluent from such a treatment of waste sulfite liquor will show a t least 75 per cent, and probably materially more, reduction in oxygen demand as compared with the untreated liquors. Toxicity Tests
The tests as to the relative toxicity are not completed, but point toward a similar reduction for the treated liquors as against the untreated. Whatever toxicity the waste sulfite liquor may have is most likely to reside in its lignin component, and it is the lignin component that is removed by this treatment. Also the lignin substance thus removed shows an appreciable toxicity. Tests are now under way which will give additional evidence on the relative toxicity of the treated and untreated liquors as judged by the tolerance of fish life when exposed to these liquors. Results to date indicate a material reduction in toxicity in favor of the treated liquors, and if the final results confirm this it will likewise point to the lignin substance being the toxic component. Theoretical Explanation of T r e a t m e n t
The question naturally arises as to why this fractional precipitation treatment should effect such a radical reduction in the oxygen demand of waste sulfite liquor. Apparently this is due primarily to the removal of the lignin component of the liquors and incidentally to the fact that the carbohydrates remaining in the tail liquors are evidently stabilized against oxidation by being organically combined with sulfur, for example, as an aldehyde addition product, the ionization of which is in turn suppressed by other components of the system. Ample evidence has been obtained that the lignin substance is oxidizable under certain circumstances even to the extent of absorbing oxygen from the air, and its probable structure is also in line with this property. Hence it is reasonable to expect its removal to reduce the oxygen demand. Some organic constituent must be responsible, since the oxidation of all the sulfur content in sulfite liquor will account for only a minor part of its oxygen demand. Whether the carbohydrates were organically combined with sulfur in the untreated liquor or acquire this combination during the treatment, has not been determined with certainty, It is conceivable that such combinations could form during the treatment process. On the other hand, it seems more likely that these carbohydrates are, in part a t least, organically combined with sulfur as the liquors come from the digester, the extent depending on the amount of base present in the cooking acid relative to the requirements for such base to satisfy the dominant demand of the lignin sulfonic acid for the base, and that only the base present in excess of such requirement is available to permit the formation of stable combinations with Carbohydrates.
Potassium Chlorate Subject to Explosives Tax in Cuba I n Circular 26, March 8, 1930, the Cuban Treasury Department has ruled that, except when imported by druggists for pharmaceutical purposes, in quantities not exceeding 100 pounds, potassium chlorate is subject to the explosives tax of $1.00 per 100 pounds, in addition t o the regular import duty of $1.26 per 100 gross kilograms when imported from the United States, plus a surtax of 3 per cent of duty.
