The steam condensates from the reciprocating engines of small aircraft carriers and transports contain some of the lubricating oil in the form of an emulsion. This oil must be removed by filters before the water can be used again in the ship's boilers. Consequently, turbidimeters and turbidity standards are needed for determining the amount of emulsified oil in the steam condensates and clarified filtrates.
At the request of the Research Section of the Navy Bureau of Ships, George G. Manov, N. J. DeLollis, and S. F. Acree, of the National Bureau of Standards, undertook in May, I943, the development and production of standards of turbidity for oil-in-water emulsions ranging from o to 2 parts per million oil, that would deteriorate as little as possible during a 6-month period. It was further requested that an effort be made to stimulate the development and production of shipboard turbidimeters by manufacturers, and that the resulting instruments be tested at the Bureau for compliance with performance specifications set up jointly by the Bureau of Ships and the Bureau of Standards.
Six commercial and laboratory type turbidimeters were tested as to suitability for use on board rolling, vibrating ships under the conditions of high temperatures and humidities usually present in the engine rooms. Turbidimeters with photocells and galvanometer or "magiceye" balance detectors were studied and calibrated with various turbidity standards. In the most successful instrument two opposing photocells are used to measure the difference in light transmission of air and of turbidity standards or of a cuvette containing the test sample. A "magic-eye" tube serves to detect the balance point. The meter is rugged, portable, and plugs into any IIO-v. a.c. line for operation. It is insensitive to tilting, vibration, and shock, and may be calibrated readily by any of the types of standards developed at the Bureau. The readings of the instrument are reproducible to :k o.o 5 p.p.m, oil and the steadiness appears to be qui!~e satisfactory. The calibration of the scale, which can be graduated to read directly in p.p.m., is linear and does not shift with time. Likewise, a humidity oI~ Ioo per cent. does not affect the operation of the electrical circuits of the turbidimeter.
Three types of turbidity standards that can be turned out by mass * Communicated by the Director.
4TI