A Compact Field Laboratory for Sanitary Chemistrv r,
JAMES G. WEART, Illinois Department of Public Health, Springfield, Ill.
T
HIS field laboratory was designed for the use of sanitary
test, the amount of indicator supplied is ample. This type of p H equipment was designed about ten years ago at the laboratories of the Sanitary District of Chicago, The regular Winkler method is used for dissolved oxygen. The reagents are in Pyrex dilution bottles of 180-ml. capacity, and are dispensed by a Pyrex pipet graduated a t 0.5 and 1.0 ml., fitted in a rubber stopper, and operated by a rubber bulb. Two ll&ml. (4ounce) ground-glass stoppered bottles, graduated at 100 ml., are provided for the collection of samples and for the test. Sulfuric acid is supplied in 50 per cent strength, rather than concentrated, so that 1 ml. can be added to fill the neck of the bottle. Fifty to sixty dissolved oxygen determinations can be made with the solutions provided. Alkalinity and soap hardness are determined according to standard methods (9). For themeasurement of samples there are a graduate and a calibrated bottle. Distilled water is available for dilution purposes. Free carbon dioxide can be calculated from the alblinity and pH, according to the formula of DeMartini ( 1 ) :
engineers engaged in the wide variety of problems encountered b y the Department of Public Health and the State Sanitary Water Board. These problems include the supervision of all types of water-treatment plants and sewage plants, and the investigation of industrial wastes and stream pollution. For these purposes, the kit pas designed to permit the following tests: pH, dissolved oxygen, alkalinity, soap hardness, residual chlorine, carbon dioxide, and temperature. Sufficient extra capacity is provided so that i t can be readily adapted to test for iron, nitrites, copper, or ammonia.
Apparatus and Methods The case is substantial. Top, sides, and bottom are constructed of 1.25-cm. (0.5-inch) birch. The finish inside and out is acid- and alkali-resistant. A full-length piano hinge and trunk clas s support the cover. A11 corners are closed with a lock or pin {ox joint. Top and bottom corners are protected with trunk corners. In the field, a clean work table is provided by the lid of the case, which is supported by two metal rods which screw into metal floor sockets. The inside of the lid is covered with white celluloid. T h e buret support rod is wrewed into another floor socket. The buret clamp is readily attached. F o r b u r e t s , 10-ml. serological pipets are adapted by a modification of an old device, a bead in a rubber tube. The bead is located a t the upper end of the ipet instead of a t the Eottom. This permits easy filling and excellent control during titrations. There are no stopcocks to break. Three of these pipetburets, one for each of the three standard solutions, are held by clips in the removable tray. The test most frequently made in this work is the determination of pH. The kit provides for the colorimetric determination of pH over the range of 4.0 to 11.0, in steps of 0.2 pH. For demonstration tests and approximations, a wide-range indicator is provided. In the range from pH 6.4 to 8.4, which is used m o s t f r e q u e n t l y . the two indicators required are supplied in 59-ml. (2-ounce) bottles. All other indicators are in 29.6-m1. (1-ounce) bottles. As but one or two drops of indicator a r e needed f o r each
log CO:
-
6.2874 f log (HCOa- a8 CaCOa)
- pH
A slide rule or a log table is, of course, necessary. For residual chlorine, standards prepared from Scott's buffered chromate-dichromate solutions are provided. The o-tolidine furnished contains 20 per cent hydrochloric acid. Tests are made in 59-ml. (2-ounce) oil sample bottles. For adaptions t o special work, two dropping bottles, three 59-ml. (2-ounce) oil sample bottles, and one dilution bottle are provided as surplus. Two spare dosing pipets with bulb and rubber stopper are included. The kits were prepared by Rascher & Betzold at a cost of $90 e a c h in lots of t e n . The weight is 13.6 kg. (30 pounds).
No claim for perfection is made, and suggest'ions, f o r i m p r o v e m e n t a r e invited.
Literature Cited 11) DeMartini, F. E., J . Am. Water Works A s s o c . , 30, 105 (1938). (2) "Standard
Methods
of Water Analysis,"
New York, American Public Health Assoc., 1936. RBCEIVED September 12, 1938. Presented before the Diviaion of Water, Sewage, and Sanitation Chemistry a t the 96th Meeting of the American Chemical Society, Milwaukee, Wis., September 5 to Q, 1938.
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