tie oil comes with it, it is removed by filtering through dry filter paper. An aliquot part, depending on the salt content, is then concentrated for titration with a solution of approximately 0.05 N silver nitrate, using potassium chromate as an indicator.From these results the chlorine can be calculated, or, if previous analysis of similar brine has shown it to consist mostly of sodium chloride, it may be calculated as such.We have tested the accuracy of the method by making a re-treatment of some of the oil which had settled out after the treatment outlined above. A mere trace of chlorides could be found, thus furnishing good proof that the first treatment had effected their almost com-

No abstract

No abstract

No abstract

Biofouling presents a significant obstacle to the long-term use of electrochemical sensors in complex media. Drinking water biofilms reduce performance of sensors by insulating electrode surfaces by inter alia inhibiting mass transport. Boron-doped diamond (BDD) electrodes are relatively resistant to biofouling and inert at high potentials. These qualities can be exploited to create a drinking water quality sensor that resists biofouling to meet performance criteria for longer, and to enable electrochemical cleaning of the sensor surface in situ using high potentials without disconnecting or disassembling the sensor. A purpose-built BDD wall-jet sensor was compared with a glassy carbon (GC) sensor in ability to determine free chlorine, detect biofilm and remove biofilm in situ. It was found that the BDD produced accurate and reliable readings with a 4.86% standard error and a LOD of 0.18 ppm. The BDD could be electrochemically cleaned in situ whereas this was less successful with the GC electrode. The BDD electrode could also detect electroactive pyocyanin, secreted in the biofilm of the drinking water biofilm indicator organism Pseudomonas aeruginosa, potentially enabling biofouling and non-biological fouling such as scaling to be distinguished. Observed changes in flow sensitivity and current-voltage curves that correspond to fouling provide multiple fouling detection methods, resulting in an accurate, sensitive, water quality sensor that can be cleaned without disassembly or replacement of parts and can identify when cleaning is required