MARCH 15,1940
ANALYTICAL EDITIOA
IS9
sample of the mater. Accordiiig to the3e ~nvestigatorsthr. presence of very small quantities 0' one or more of the following metals may be detected with this method: zinc, copper, lead, nickel, cobalt, mercury, cac'mium, thallium, and bismuth. I n the authors' case, the impurities n; inld probably be copper, lead, and zinc. It has been found, in this laboratory, t metals listed above do not display equal a11 the test color with dithizone, the method of' testing is very sensitive. Using care, it is posdile to detect as little as 0.1 microgram of zinc, rvhich agrees i x t h the clainis of Stout and Arnon. Using a standard solutio11 of zinc. and comparing thr color developed by clithizoiie with 1;he standard and wiDh that produced with the concentrate from 2 liters c;f distilled water. using a microcolorimeter, it was found that the distilled water contained 0.2 part per billion of total metals (as listed above). The conductance of a sample of the distilled r a t e r was measured, taking no special precaution to esulude carbon dioxide or fumes generally present in a chemical laboratory. The specific conchctance, as measured, TT':LS 2.88 X reciprocal ohm. From the above tests, tlie authors are of the opinion that the distilled water produced by t'hk still can br regarded as free from metallic' compounds as it is posi:ible to produce mater in the quantity shown with Y single distillation. I n investigations prrtaininp to ilie study of the effects of the minor elements on gron?h s.nd development, of both plants and animals, large volumes of clistilleti Jvater are consumed daily. Because distillation of miter f , m m an ordinary still would be both t,irne-consuming and trou.blesome, such a strill as has been dw(:rihed a1m-e j c of great, importance.
Literature Cited (1) Stout, P. R.,and . I m o n , D. I., Am,. .T. Rotan!/, 26,144-9 (1939)
FIGURE 3. STILL INSTALLEI) 1. Drain from sweat pan 2. Valve f o r cleaning o u t condenser jacket 3. Valve regulating flow of water into condenser jacket 4. Drain pipe for boiler 5 . Steam inlet valve 6. Clean-out valve for boiler
days in succession. The reservoirs were placed in a leadlined basin, which was connected to a drain pipe in caw of overflow.
A Ten-Liter Volumetric Flask FRANCIS ,J. REJTHEL
Tests for Purity of Distillate After the still had been in operation for several months a sample of distilled water was collected in a thoroughly cleaned Pyres flask. A 3.5-liter portion of the sample was evaporated to a small volume in a new Pyrex glass flask, which was attached to a condenser with a ground-glass connection. The concentrate was transferred t o a weighed platinum dish and evaporated t o drynew in an oven. The following results were obtained: Total solids (evaporated a t 110' C.), 0.00029 gram Ignited solids (750' C i,0.0001 gram per liter
THE investigation reported here was carried out in connection with a project of the Kentucky Agricultural Experiment Station, Lexington. Ky.. and is piihlished by t h e prrmission of i h e Director
liter
Another test was made on a 10-liter sample of water, using the above-described technique, with the following results: Total solids (evaporated a t 110' C.), 0.00037 gram per liter Ignited solids (750' C.), 0.00015 gram per liter
The reaults of this last test are equivalent to 150 p. p. b. of ignited total solids. Most of this residue was silica which had been dissolved from the condenser tube and Pyrex flask used in concentrating. A negative test for iron in the water was obtained, using the sulfocyanate method, indicating that iron, if preqent a t all, &-asless than 0.5 part per billion, which is the limit of sensitivity of the test. The dithizone test for "total metals'' described b y Stout and .irnon ( 1 ) was made on the cnnwntrate from a 2-liter
University of Oregon 3Iedical School, Portland. Ore.
HEX making large quantiti1.s of staniiard solutions a large volumetric flask is desirable. In the author's laboratory this is provided by fitting a 12-111rr Pyrex bottle with a simple volume indicator. A graduated pipet is inserted through a rubber stopper that is large enough to rest flat on the neck of the bottle. Exactly 10 liters of mater (or any other desired volume) a t room temperature are put into the bottle, arid the pipet is adjusted so that the tip barely touches the surface of tlie liquid. If a 10-ml. pipet is used, the graduations near the top will be partly covered b y the stoppel, b) that whcn thP pipet just touches the surface of the liquid the, lon-er surface of the stopper will correspond to some reading on the pipet-say, 2.2 ml. The pipet can be readjusted in;tantaneously by resetting the loner surface of the stopper to the propel mark. Any volume in the flask will corre-pond to a mark on the pipet, the readings becoming greater witli larger volumes as the pipet is pushed up through tlie stopper, and a eimplr table may be prepared shoving r d i n g s for \ arious volumes The pipet itself is never immersed in the liquid. \Then the apparatus is carefully adjiistetl, t h c volume can he measured tn * 5 ml.
