Continuous Monitoring System for the Wastewaters Having Multiply, Randomly, and Small Effluent Characteristics -Approarch to Analysis of Chemical Oxygen Demand by Complete Flow Process-

A simple system was developed for the fully automatic and continuous measurement of chemical oxygen demand (COD) in wastewater samples based on colorimetry of dichromate. A sample and a solution of sulfuric acid (1+1) containing 2mM potassium dichromate are continuously pumped with a double-reciprocating micro-pump at each flow rate of 0.3 ml/min. The wastewater sample is filtered at first with a 100-mesh stainless filter and then mixed with the dichromate solution in the mixing joint. The mixture is introduced into a reaction coil made of poly(tetrafluoroethylene) tubing (1 mm i.d., 3 mm o.d., and 20 m length), being placed in an oil bath (120℃). After reaction, the mixture passes into a quartz tubular flow-through cell (10 mm path length, 18 μl volume) in a spectrophotometer, and the absorbance is measured at 445 nm. The COD value of the sample is automatically estimated from the amount of decreased absorbance. The system was successfully applied to COD measurement of some waters, and to continuous monitoring of COD in wastewater of university laboratories. The system was also evaluated by comparing with the flow injection analyzer system previously developed by the authors

Condensation of Ketones and t-ButyI Haloacetates in the Presence of Aluminum or Lithium

The Reformatsky reaction with t-butyl haloacetate could be effected in the presence of lithium or aluminum, but the latter metal proved to be disappointing as a condensing agent. Condensation of benzophenone with t-butyl chloroacetate and bromoacetate in the presence of lithium gave corresponding β-hydroxy esters in yields of 43 and 58%, respectively, and comparable with those of other condensing methods

Condensation of Ketones and t-Butyl Chloroacetate in the Presence of Magnesium.

Condensation of σt -butyl chloroacetate and ketones by means of magnesium in ether or benzene alone was carried out but the excellent yields of P-hydroxy ester could not be obtained, and the results of the condensation of t -butyl bromoacetate and ketones by means of magnesium and mercuric chloride in benzene were also disappointing. When a mixture of benzene and ether was used as solvent in the condensation of t-butyl chloroacetate and ketone in the presence of magnesium and mercuric chloride, the yields of p-hydroxy esters from cyclohexanone and methyl isobutyl ketone were 62 and 71 % respectively, and were comparable with those of other condensing methods

Studies on Oxasteroids. I. Synthesis of 3-Cyano-3-methylchroman-4-one.

Condensation of chroman-4-one with ethyl formate in the presence of sodium methoxide gave 3-hydroxymethylenechroman-4-one (II). Reaction of II with hydroxylamine hydrochloride, followed isomerization by potassium t-butoxide gave IV. 3-Cyano-3-methylchroman-4-one was obtained by methylation of IV or treatment of III with potassium t-butoxide and methyl iodide

Evaluation of Three Flow Injection Analysis Methods for the Determination of Chemical Oxygen Demand

Three methods for determining chemical oxygen demand (COD) by means of flow injection analysis (FIA) with potassium permanganate, potassium dichromate, or cerium(IV) sulfate as oxidant, developed in this laboratory, are described from the point of view of their operating properties. The permanganate method is the most sensitive and common, but forms manganese(IV) oxide precipitate which blocks the FIA lines and connectors. Addition of phosphoric acid in the reagent system is, however, effective to some extent in order to avoid blocking the flow system. The dichromate method is the most workable and stable, but produces toxic wastes containing chromium(VI). The cerium method is the most probable because cerium(IV) is the strongest oxidant of the three and less poisonous. The last method with cerium(IV) sulfate is therefore recommendable to apply to the continuous monitoring of COD in many situation

Improved Method for the Flow Injection Analysis of Chemical Oxygen Demand Using Silver Nitrate

On the flow injection analysis (FIA) of chemical oxygen demand (COD), silver salt was added as an oxidation catalyst for COD substances and a masking agent for halide to improve operating conditions of the FIA apparatus. Both of a proper concentration of potassium permanganate solution and 6.0 % sulfuric acid solution containing 0.1 % silver nitrate are individually pumped up with respective flow rates of 0.51 ml min(-l) and merged into a carrier stream. A 20 μ1 of sample solution is injected into the flow of sulfuric acid solution at just before the merging place. The sample mixed with the carrier solutions in a reaction manifol(polytetrafluoroethylene tubing: 0.5 mm i.d. x 30 m), is passed through a thermostated bath at 100 °c and led to a flow cell for the absorbance measurements at 525 nm. The absorbances are continuously recorded with time. The peaks in the recordings showed good reproducibility and the calibration obtained at a linear concentration range of 0 - 170 mg 1(-1) COD with glucose as standard. The detection limit and precision confirmed with this method were 5 mg 1(-1) and 0.8 %, respectively. Chloride ion up to 200 mg 1(-1) did not interfere without elimination of a silver chloride precipitate. By the present FIA method, several industrial waste water samples were analyzed at a sampling rate of about 40 samples per hour, and their apparent COD values were compared with those found by the manual JIS method. Both of the methods gave the similar results within an error range from -35 to +5 %