April, 1945
ANALYTICAL EDITION
of tile electrolyte; after removal of the electrodes, ammonium liydroside was adtletl. Approximately one ampere-hour would Ijr rcquireti electrically t o deposit the copper and lead from 1 gritiii of bronze but the average value for laboratory practice is 1.5 :mipere-liours. Using 1.75 amperes 1)er electrolyte, the first three examples compare the time of depo.?ition with air stirring plus sulfamic aciti; air stirring without sulfamic acid; and no air stirring, no sulfaniir acid, respectively. The fourth uses urea on a set of boiled nitric acid samples; the fifth uses starch, illustrating a n atitlitive reagent Lvhich may be considered aj aldehyde, ketone, aliwiiol, and organic chemical. Example 6 represents the longest time required to plate tbventy-four samples siinultaneously a t i to 1.25 amperes. Standard-size platinum gauze electrodes, 200w. heaker.4, and 110 cc. of electrolyte were used. The use of sulfnrnie acid, with or without air stirrin:, results in firin and adherent coats of metallic copper and lead peroxide. Recomniended procedure is: solution of the bronze in nitric acid, removal of tin oxide, if any, electrodeposition of copper and lead during which sulfuric acid is added, and finally addition of an
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aqueous solution of sulfamic acid. 15 minutes before removing the electrolyte. T h e amount of sulfamic acid required is 0.25 to 0.5 gram (loyoaqueous solution) per electrolyte. The electrodeposition of copper in the presence of a very small amount of chloride ion has been recommended ( I ) . However, the effectiveness of the simultaneous use of chloride ion and sulfamic acid was not studied. A complete description of the preparation and properties (3,4,5 ) of sulfamic acid may be found in t h e literature. ACKNOWLEDGMENTS
To Wni. B. Goodman, Ann Kukic, and W. Cawy for assistance in experimental determinations. L I T E R A T U R E CITED
A.S.T.11. Methods, Chemical Analysis of Metals, p. 170 (1943). Baumgarten, P., and Marggraff, I., Ber.. 63, 1019 (1930). Clapp. L. B., J . Chem. Educatzon. 20, 189 (1943). Cupery, 31.E., IND.ENO.CHEM., 30. 627 (1938). Gordon, W. E., and Cupery, M .E., Ibid., 31, 1237 (1939): 34,
792 (1942).
Removing Samples of Filtrate without Interrupting Suction M. S. TELANG Laxrninarayan Institute of Technology, Nagpur University, Nagpur, India
DIFI;I('CLTIES
are often experienced when testing for the cornplcteness of washing of a precipitate using suction, as there 1 1 s h w n no simple device by which to tost t h t filtrate witho u t disturbing thcl various leakproof connrctionu. The apparatus clcwribed here sueccs~fullgmeeta these difficulties arid can be c.a-.ily prcpnred from materials readily available in a good laboratory.
a
T o start filtering, y (Figure 1) should be closed, .with h open. T h e filtrate will be collectcd in k. When testing for completeness of washirig, h. should he closed, suction being continued through by-pass d . After a sufficient quantity of filtrate has collected in the lon-er portion of the adapter, vacuum is temporarily broken by opening I , and g is opened t o withdraw the filtrate coliected in e and j" into a test tube for testing with the necessary reagent. If washing and filtration should he continued further, g and I are closed and h is opened. Since side a r m f m a y contain filtrate from an earlier washing, a t every opening of g the first few milliliters of the liquid should be rejected bcfore testing. A sufficient quantity of filtrate can be obtained quickly without any disconneetions.
C-
(Left) Funnel with filter paper cone b. Platinum cone filter support c. Rubber stopper d . By-pass tube to continue suction when h is closed e. G o o c h crucible adapter f. Side arm fused to stem of adapter to withdraw collected liauid when h is closed g. Short rubber tube with pinchcock h. Short rubber tube with screw pincha.
-
=lama ._...
Glass tube Rubber stopper k. Filter Rask 1. T-piece with pinchcock and rubber tube to break vacuum W h o l e supported by suitable clamps
1. j .
U Figure 2. All-Glass Apparatus
A corresponding all-glass apparatus, shown in Figure 2, can be made froin a Gooch crucible adapter and a three-way stopcock by any skilled g1a.c blower. I t s o p e r a t i o n is self-evident; parts c o r r e s p o n d i n g t o those in Figure I art> indicated in Figure 2 . For constant use this pattern is more convenii~ntt!-ian t h a t of Figure 1, and has the,advantage that it can also be used for Gooch crucibles. T h e deirice can be used as a supplementary piece of apparatus for vacuum filtration techniqiit: ( 1 , 2 ) .
L I T E R A T U R E CITED
1 Figure 1 .
PWP Apparatus
(1) Clowes and Coleman, "Quantitative Chemical Analysis", p. 48, London. d. & A. Churchill, 19.38. ( 2 ) Cummirig and Kay, "Quantitative Chemical Akmiysis". p . 33, London, Gurney & Jackson, 1934.
