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New methods and modifications of known methods of detecting arsenic and selenium in water are described. Whereas the previous procedures for these elements are extremely tedious and time consuming, these new procedures can be performed in a few minutes—thereby permitting routine monitoring of water supplies for As and Se.

This study provided data for the evaluation of some of the methods currently in use for the determination of minerals in water. The study also indicated the degree of accuracy and precision obtainable when many laboratories participate and a variety of methods are used. Nitrate determinations were the least accurate, and the nitrite measurement was only slightly better than the nitrate. Other determinations showed substantial improvement over the results of earlier studies. With the exception of the nitrogen measurements, overall precision and accuracy are excellent, especially for so large a number of participants working with so wide a choice of methods.

This study has found that the silver diethyldithiocarbamate method for arsenic is superior to the heteropoly blue method in time of analysis and ease of manipulation, and is superior to both the Gutzeit and the heteropoly blue methods in precision and accuracy. The procedure is applicable to the measurement of arsenic in the range of public health interest in raw river waters, finished water, and domestic sewage and is unaffected by wide variations in mineral and organic content of the sample.