Readily Carbonizable Substances

Recognizing the need for a more economically and environmentally friendly citric acid recovery process, an adsorptive separation process to recover citric acid from fermentation broth was developed by UOP [9-14] using resin adsorbents. No waste gypsum is generated with the adsorption technique. The citric acid product recovered from the Sorbex pilot plant either met or exceeded all specifications, including that for readily carbonizable substances. An analysis of the citric acid product generated from a commercially prepared fermentation broth is shown in Table 6.2, along with typical production specifications. The example sited here is not related to zeolite separation. It is intent to demonstrate the impact of adsorption to other separation processes. 

Readily Carbonizable Substances Determine as directed under Readily Carbonizable Substances, Appendix IIB, using 200 mg of sample dissolved in 5 mL of 95% sulfuric acid and kept at 48° to 50° for 10 min. The color is no darker than that of Matching Fluid A. 

Color A sample shows no more color than does Matching Fluid A under Readily Carbonizable Substances, Appendix 11 li. 

Readily Carbonizable Substances. .. 845 Chloride Limit Test... 863... 

Colorimetric solutions are used in the preparation of colorimetric standards for certain chemicals and for the carbonization tests with sulfuric acid that are specified in several monographs. Directions for the preparation of the primary colorimetric solutions and Matching Fluids are given under the test for Readily Carbonizable Substances, Appendix IIB. Store the solutions in suitably resistant, tight containers. 

Revision Description revised Heavy Metals (as Pb) and Ultraviolet Absorbance specifications and determinations deleted Tridodecylamine specification revised Readily Carbonizable Substances test replaced Residue on Ignition test reworded. ... 

Readily Carbonizable Substances Transfer 1.00 + 0.01 g of finely powdered Citric Acid to a 150-mm x 18-mm (od) tube previously rinsed with 10 mL of 98% sulfuric acid at 90° or used exclusively for this test. Add 10 + 0.1 mL of 98% sulfuric acid, carefully agitate the tube until solution is complete, and immerse the tube in a water bath at 90° + 1° for 1 h. Occasionally remove the tube from the water bath and carefully agitate it to ensure that the Citric Acid is dissolved and gaseous decomposition products are allowed to escape to the atmosphere. Cool the tube to ambient temperature, carefully shake the tube to ensure that all gases are removed, and using an adequate spectrophotometer, measure the absorbance and transmission of the solution at 470 nm in a 1-cm cell. The absorbance does not exceed 0.52, and the transmission is equal to or exceeds 30%. 

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