ANALYTICAL EDI T I O S
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The solution when being tested for molybdate ion must be either neutral or slightly alkaline. It must not be very acid or the indicator loses its sensitivity. I n an acid solution the concentration of the molybdate must reach 0.002 normal before it can be det'ected. The color which forms. IiorTever, is the same as in a neutral or alkaline solution. The solution being tested must not hal-e a high coiicentration of hydroxyl ions, for the hydroxyl ion itself will cause the brown colorat'ion to appear. Ammonium salts have no effect on the indicator, nor does the precipitated lead molybdate. I n contact with a fairly concentrated solution of the molybdate ion, say 0.1 normal. the indicator shows a deep reddish brown color. Since many molybdates are insoluble, the indicator herein
1-01, 2 ,
so. 4
described should form a basis for other voluiiietric molybdate methods. I t might also form the basis for the determination of molybdenum colorimetrically. Conclusions
The results obtained by the volumetric method check very closely x i t h those obtained by the gravimetric method. but the time required is much less by the volumetric method. A saturated solution of pyrogallol in chloroform is a very sensitive indicator for the molybdate ion. An aqueous solution of pyrogallol is much less sensitive than a chloroform solution. Literature Cited (1) \Viler. IKD.EXG.CHEM, Anal. Ed., 2 , 124 (1930).
Identification of Aluminum and Magnesium in Printing Inks' Louis M . Larsen INTRRXATIONAL PRINTING1.-
ONCENTR.4TED printing inks are frequently extended with transparent inks to improve their printing qualities, and a t the same time to arrive a t a reasonable cost. The important transparent extenders are precipitated aluminum hydroxide and precipitated magnesium carbonate. Barium sulfate is also a popular extender, but it belongs to the semi-opaque type of inks. Kot only is aluminum hydroxide used as an extender, but it is often used as a substratum upon which organic dyestuffs are precipitated producing lake pigments. Furthermore, ultramarine blue, aluminum phosphate, and some aluminum lakes contain aluminum in other forms than the hydroxide. Aluminum powder itself is used as the pigment in so-called silver inks. It is obvious, therefore, that aluminum may be present in the final ink in a variety of forms, but usually as the hydroxide. Magnesium is very rarely present in inks except as the carbonate. The identification of both aluminum and magnesium involves the use of lake-forming dyestuffs, capable of detecting small quantities of the above elements in the presence of other ingredients used in inks. These dyestuffs are aluminon ( 2 , 5 ) for aluminum, and benzopurpurine 4B (1) for magnesium.
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Preparation of Test Strips Inasinuch as nearly all of the paper manufactured today has been treated with an alum solution, a paper that is free from aluminum must be used in order that this element may be properly identified. I t is not necessary, however, t o employ a special paper for the detection of magnesium. I n order to prevent the formation of pigment suspensions and even colloidal solutions, it is advantageous to add some highly viscous linseed varnish, together with a small percentage of a concentrated cobalt drier (4 per cent cobalt) to the ink before printing. The oxidation of the linseed varnish to insoluble linoxyn keeps the pigment from floating out mechanically. The modified ink is then either printed on paper using a proof press or pulled down as evenly as possible on the paper with a steel scraper. The rate of oxidation (drying) can be increased by placing the prints in an electric o\-en at 70" C. After the prints have become dry by oxidation, they are cut 1R
CCUT July ~ 7, 19SO.
CORPORATION, SEW YORK, IY. x.
up into strips ("8 by l l / z inches) using a photo card trimmer. Each strip is marked by a pencil for identification. Procedure for Aluminum Place four dried test strips in a test tube and cover half with a 2 N solution of hydrochloric acid. Boil gently, with shaking, for 1 minute. Pour the extract into another test tube and cool, leaving the paper strips behind. If not clear, filter. Determine whether or not' iron is present before proceeding further. Dilute 1 cc. of the extract with 10 cc. of distilled water, add R few drops of a 5 per cent solution of potassium ferrocyanide solution, and shake. A distinct blue indicates the presence of appreciable amounts of iron. If there is not more than a trace of iron, as is the case in 98 per cent of the inks, continue the test for aluminum. To the clear acid extract add an equal volume of a special aluminon reagent,2 and mix well. Warm cautiously to boiling, avoiding bumping as much as possible, and boil gently for 1 minute. Allow to stand in a rack for 5 minut'es longer to promote identification of traces. h deep red flocculent precipitate indicates that aluminum is present. Absence of a precipitate indicates that aluminum is absent above minute trace (possibly 1per cext in inks). Add to the cooled solution containing the precipitate an equal yolume of a prepared alkaline aminoniuiii carbonate s ~ l u t i o n . ~If the precipitate is unchanged after thorough shaking in the cold, report, aluminum as being present in the ink. Should the solution be highly colored before or after the addition of the alkaline solution, filtration followed by washing with distilled water and later denatured alcohol will usually make it possible to inspect the color of the precipitate. If desired, the entire process of reprecipitation, etc., can be applied t,o the contaminated precipitate, yielding a purer precipitate, more suitable for observation. Procedure for Magnesium Place four dried test strips in a test tube and boil with a 5 per cent acetic acid solution for 2 minutes. Pour the acid 8 290 grams crystalline ammonium acetate, 10 grams glacial acetic acid, and 1 gram aurin tricarboxylic acid, diluted with distilled water t o a liter. 8 100 grams ammonium carbonate, 50 cc. concentrated ammonia water, 850 cc. distilled wster.
INDliSTRI.4L A.VD ENGILYEERI-VG CHE-IIISTRY
October 15, 1930
extract into another test tube, leaving the paper strips behind. Some pigments produce colored solutions which interfere with the subsequent color test for magnesium. I n such cases decolorize by adding a few drops of a fresh 2 per cent chloramine T solution a t the boiling point. Avoid a n excess unless the color is very hard to destroy. Disregard the white precipitate which may show up on cooling. Treat the cooled extract with an equal volunie of a 5 per cent caustic soda solution which is clear and free from sediment. Simultaneously run a blank, omitting the test strips. To each add a drop of benzopurpurine 4B dye4reagent for every cubic centimeter of solution. Shake and let stand from 2 to 5 minutes, but do not raise the temperature. A distinct rose-colored precipitate indicates the presence of magnesium. Minute traces of mag4 Benzopurpurine 4 8 can be secured from the Newport Chemical Cornpany. It is dissolved in distilled water using 1 gram of the dye to 4 liters of distilled water.
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nesium from other sources as well as from the ink itself may show up as a weak red coloration. Application to Dry Pigments
Pigments, as well as inks, can be examined for aluminum and magnesium by converting them into inks and then a p plying the analysis. The pigment is rubbed well with a viscous linseed varnish on a glass slab, and treated with a small amount of cobalt drier. I n this manner fine pigment,s lose their tendency to form colloidal solutions. Literature Cited (1) Eergriwe, Z.anal. Ckem., 76, 354 (1929). (21 Hammett and Sottery, J , A m . C k c n . SOC.,47, 143 (192.5). (3) Winter, Thrun, and Bird, Ibid., 61, 2721 (1929).
Convenient Accessories for Use with the Saybolt Universal Viscometer' Carl Winning STAXDARD OIL DEVELOPMENT COMPANY, ELIZABETH, ii. J.
HE Saybolt Universal viscometer. which is the standard
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instrument used in the United States for testing lubricating oils and certain other petroleum products, is ordinarily operated in accordance with a n inflexible set of rules. These rules, as well a9 the essential details and dimensions of the apparatus, have been standardized by the American Society for Testing Materials ( 2 ) for the purpose of insuring agreement among the results of various operators, and the lack of flexibility is a necessary feature. The Saybolt Furol v i s c o m e t e r \vas developed and has been similarly standardized to handle highviscosity fuel oils and road oils a t moderately low t e m p e r a t u r e s . Various special viscometers have been used to meet conditions which fall outside the range provided for by the A. S. T. &I. methods. The d e v i c e s described in this paper adapt the Saybolt Universal viscometer, with its ordinary accessory equipment, to two sets of conditions frequently encountered in oiltesting laboratories. Testing of Small Samples
Figure 1-Adaptor to Perm i t Testing Small Quantit i e s of Oil i n t h e Saybolt Universal Viscometer A-1.111 cm.: B--12.50 cm. Dimensions A and B determine the constants of the modified viscometer.
T h e m i n i m u m quantity of oil that can be tested in a Saybolt Universal viscometer is of the order of 80 cc. It is frequently necessary to determine the viscosity of smaller samples and various types of glass and metal micro-viscometers are employed. The Adkins instrument ( 1 ) is typical and has the advantage of being made with 1
Received July 5, 1930.
the same over-all dimensions as the Saybolt tube, which permits interchangeable use in the same bath. The adaptor illustrated in Figure 1 is less expensive than the Adkins micro-viscometer and its use does not necessitate even the labor incident to changing tubes in a bath. (The average petroleum laboratory is not required to test a sufficient number of undersize samples to warrant maintaining a micro-viscometer in a n individual bath with the desirable accessories for stirring and thermostatic control.) The adaptor is a metal plug which can be slipped into a standard Saybolt Universal (or Furol) tube and, when made with the dimensions shown in Figure 1, it reduces the volume of the sample required t o 15 cc. The adaptor must be machined to fit a particular tube. The general operating procedure is the same as for the usual sized sample, the time required for 8 cc. of oil to flow into a suitable receiving graduate being measured. Table I shows the data obtained in calibrating a n adaptor used in the writer's laboratory. From these data it is possible to prepare conversion charts or tables of the particular type vhich may be preferred b y the users of the instrument. It has not been considered necessary to adjust adaptors to any fixed calibration curve, and machining to closer dimensional t o l e r a n c e s t h a n a r e maintained in ordinary shop practice is thus avoided. Each adaptor will, of course, require I C M I.D. i n d i v i d u a l calibration. The a c c u r a c y attainable through m use of the adaptor, although adequate for ordinary requirements, is obvious!y less than that of the standard method, and the use of this device is ~-4.1 A not recommended except for Figure 2-Form a n d Approxim a t e D i m e n s l o n s of 28.6 cc. cases of necessity. Saybolt Viscosity Flask
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