March, 1924
INDUSTRIAL ,450 ESGIXEERISG CHE.1fISTRY
calibration curve is needed. Data for such a curve are given in Table I11 and the resulting curve is given in Figure 2 (Curve B). It will be noted that all the liquids check this line, regardless of their surface tension. Table III-Saybolt-Thermo Times vs. Kinematic Viscosities (Corrected for capillarity) t LIQVID Z/s Seconds log Z/s log 1 Acetone 0.4150 14.0 1.618 1.146 Petroleum ether 0.4450 14.9 1.648 1.173 0.5988 19.1 1,777 1.281 Carbon tetrachloride 1.398 0.8396 25.0 i ,924 Cleaner's naphtha Water 0.9115 27.7 i.960 1.442 Kerosene 2.322 71.3 0.366 1.853
Although the Saybolt thermo-viscometer is not an instrument for precise measurement of absolute viscosities, the modified method described, together with Curve B, gives a fair approximation and may be used as such on any light liquid. Howeyer, Figure 1 applies very well to the oils for which the
293
instrument was intended, since their capillary rise (Table 11) is approximately the same. It is based upon a procedure in almost universal use in the oil industry and is therefore put forth as a simple means of securing data for calculating pressure drop and heat transfer in the practical problems of an oil refinery. Another source of error in the presentviscometer is the drainage error. Ordinarily the operator presses the bulb for only 10 or 15 seconds to clean out the capillary before making a determination; if this time is increased to 2 or 3 minutes the reading in seconds is increased, especially in the case 6f fluids more viscous than kerosene, Apparently, 10 or 15 seconds is not sufficient time for all liquid to drain from the capillary. Fortunately, however, in the case of the lighter hydrocarbons, for which the instrument was designed, this error is comparatively small.
The Shimer Filter Tube' B y Eugene C. Bingham LAFAYETTZ COI,LBGB,EASTON, PA.
ELIEVISG that it will be of considerable service to chemists to have the Shimer filter tube2made available in its improved form, the writer gives herein the specifications and details of the apparatus as it is now used in Dr. Shimer's laboratory. The apparatus shown in the figure consists of a Pyrex glass filter tube, 8,of 34 mm. outside diameter and 30 mm. inside diameter. The tube must have a uniform diameter, and for this reason the top of the tube should be ground off and not fire-polished. The stem of the tube, B , is 90 mm. long, of 10.5 mm. outqide and 9 mm. inside diameter. -4perforated glass, porcelain, or other resistant plate of 3 mm. thickness and 29 mm. in diameter is used. The perforations are numerous and should be not less than 2 mm. in diameter. The shoulder of the filter tube is made nearly flat, in order to afford a firm support for the plate. To use the tube, disks 30 mm. in diameter are cut from absorbent lint, such as is used in surgery, and one of these is placed on the supporting perforated plate. The tube is attached to a filter flask, by means of a rubber stopper, and into it is poured, under slight suction, a suspension of paper pulp made up to a creamy consistency. The excess of water is removed by suction, and when finely divided precipitates such as barium sulfate are to be filtered, the pulp is well rammed down by use of the stamper, C. For small gelatinous precipitates, and all others which never run through an ordinary filter, no stamping down is necessary. Bulky gelatinous precipitates must be filtered in the old way. The thickness of the layer of felted pulp will ordinarily be about 5 mm. When filtration and washing are completed, the handle of the stamper is run up through the stem as shown at D, and the contents of the tube are pushed cautiously upward until the filter felt just projects beyond the top of the filter tube. The felt, with its precipitate, can now be readily detached from the disk of absorbent lint and in most cases can be at once transferred in its moist state to a weighed crucible for ignition. The disk of absorbent lint can, of course, be used repeatedly.
B
Received October 8 1924, The first forms of the filter tube and detailed directions for its uoe were described by P W. Shimer. J . A m Chem. Soc , 27, 287 (1905), Chem. En&, 6, 197 (1907) I
The rod of the stamper is 210 mm. long and 8.5 mni. in diameter, and the rubber stamper is 27 mm. in its largest diameter. The end of the stamper rod must be ground off flat and true, so that the filter can be pushed out in a horizontal position, thus cleansing the sides of the tube of all adhering precipitate. Dr. Shimer has also long used successfully an alternative form of filter tube in which a perforated glass disk is made in one piece with a long glass tube. For most purposes, however, he prefers t h e f o r m herein described, since the other form is more fragile, The paper pulp can be prepared either by macerating ordinary washed p a p e r meFILTER TUBE chanically or by di30 I N S I D E DIAM gestion of unwashed 34 OUTSIDE D I A M paper for about 1 minute with pure hyFILTER M A T drochloric acid (speABSORBENT L l M T cific gravity 1.20) PERFORATED DISK slightly diluted with distilled water. The mass of paper, contained in a heavy glass or B a k e l i t e 9 HOLES vessel, must be vigor2 DlAM ously stirred with a wooden stirrer during SINSIDE DlAM the d is i n t e g r a t i n g process, and must t h e n a t once be strongly diluted with distilled water. Too long action of the strong acid must be avoided; otherwise the disintegration will
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INDUSTRIAL AND ENGINEERING CHEMISTRY
294
be carried too far and the pulp will become worthless for rapid filtration. A practically ash-free pulp can be made out of unwashed Swedish filter paper by use of a little hydrofluoric acid with the hydrochloric acid. When the mixture is used, however, it is necessary, of course, to use a ceresin, paraffincoated, or Bakelite vessel.
Vol. 17, No. 3
The advantages of this method of filtration are: (1)Effective retention of fine precipitates such as barium sulfate. (2) Rapid filtration. (3) Negligibleash whenbothacidsareusedinmakingthepulp. (4) More thorough washing of precipitates, with less wash water.
A New Method of Determining Palladium' By Herbert E. Zschiegner ROESSLER & HASLACHER C H E M I C A L CO.,PERTH AMBOY,N.J.
T IS usual in analytic practice to precipitate palladium, either as palladium cyanide, palladious iodide, or ammonium palladichloride, subsequent to the removal of platinum. Palladium may also be precipitated from the hydrochloric acid solution with dimethylglyoxime,* and in some instances is separated by selective solution (nitric acid), though the latter method is not applicable in the presence of platinum. Where these methods with the exception of the glyoxime precipitation are applied directly, without &st removing the platinum, some of the latter will be carried down, necessitating a second and even a third precipitation. On the other hand, if platinum, which may constitute 99 per cent or more of the whole, is first removed it will be likely to contain some of the palladium and will also require re-working. The separation of the platinum metals is a t best a long and tedious process, attended as it is by such disturbing factors as hydrolysis, catalysis, incomplete and reversible reactions, etc. The method here described provides for the rapid and accurate estimation of palladium directly from a solution in which platinum and other platinum metals predominate. It is especially useful where it is necessary to determine impurities in samples of technical and so-called C. P. platinum, the estimation of gold, silver, and base metal impurities being accomplished a t the same time.
I
Procedure
'
Two grams of the sample are dissolved in aqua regia and the solution is evaporated to dryness, care being taken that no metal is reduced as such. Reduction to lower chlorides may be ignored even though these are latterly more difficultly soluble in water. Neither is it necessary to eliminate nitric acid by repeated evaporation with hydrochloric acid. The residue is taken u p with 100 cc. of water and heated nearly to boiling, then removed from the heat and treated with 5 grams of sodium nitrite, stirring until the chlorides of the platinum metals are completely dissolved. The solution dears in a very few minutes, except for the precipitation of gold, which should not be confused with undissolved chlorides or products of hydrolysis. Water is then added until the volume reaches 250 cc. when another 5 grams of sodium nitrite is dissolved in the solution with stirring. The complete conversion of the chlorides to nitrites is then effected by heating gently for one hour a t a temperature not to exceed 80' C. After cooling, the solution is neutralized with normal sodium carbonate and made alkaline with a 1 2
Received October 4, 1924. Wunder and Thuringer, Z. anal. Chem , 51, 101 (1913); A n n . chim.
a m l . , 17, 201.
further addition of 0.2 CC. Alcoholic phenolphthalein is used as indicator. Gold, silver, and the base metals are precipitated. After 30 minutes these are filtered off, washed, ignited, and re-dissolved for the estimation of contained impurities. Palladium is then precipitated from the filtrate with a cold 1 per cent of dimethylglyoxime in alcohol. (Nickel, the only interfering element for the alkaline glyoxime precipitation, has been removed by the preceding operation.) Stirring hastens the precipitation of the palladium, which is then allowed to settle and coagulate for 3 hours. If less than 0.05 per cent of palladium is present, the precipitate is allowed to collect for 12 hours. The precipitate is filtered off on a weighed Gooch, washed, first with cold water, and finally with hot water, and dried a t 90" C . The precipitate is weighed as (CBHIIN40& Pd, containing 31.68 per cent palladium. It is essential that the solution be kept cool following the conversion to nitrites, else the alcohol of the phenolphthalein or of the dimethylglyoxime may cause reduction of platinum metals from the alkaline solution. Tests of Method
I n the trial tests of this method, the palladium glyoxime after weighing was ignited, reduced in hydrogen, and weighed as the metal. The composition of the (CpHI4N40&was further verified by applying the method to a sample of palladium analyzing 99 per cent pure. The sample weighed 0.0130 gram, equal to 0.01287 gram palladium. The precipitate weighed 0.0406 gram. Applying the factor 0.3168, the palladium recovery is 0.01286 gram. The accompanying table comprises the results of six tests made on a sample containing 2 grams of platinum and 0.0080 gram palladium. The platinum used contained very small quantities of iron, copper, nickel, iridium, rhodium, and ruthenium. Palladium added Gram 1 0.0080 2 n nnxn 3 0.0080 4 0.0080 5 0.0080 6 0.0080 Weighed as (CsH1bN4Ol)aPd.
No.
a
Palladium recovered'' Gram 0,0079
n nom 0.0080 0.0080
0.0081
0.0079
After weighing, the precipitates were ignited, reduced, and weighed as the metal, which was then dissolved and precipitated from hydrochloric acid solution with potassium iodide. The palladium iodide was also ignited, reduced, and weighed. I n each case the results coincided with the original figures obtained by calculating from the glyoxime.
