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Printing Inks and Their Analysis

J. B. Tuttle, W. H. Smith
1914 Journal of Industrial & Engineering Chemistry  
overcome by using for a standard a steel containing approximately t h e same amount of chromium as t h e sample. -4 still more convenient way is t o add t h e chromium as potassium bichromate, using a standard solution. so t h a t I cc. would equal 0 . o O o j gram of chromium, i. e . , o . z j per cent chromium for a 0 . 2 0 gram charge of t h e sample. This solution is added t o the standard after t h e solutions have been transferred t o t h e color comparison tubes. CHRo~fIus~LI-Weigh I
more » ... fIus~LI-Weigh I gram of the sample into a 300 cc. Erlen~lleyer flask (Jena glass). add I O O cc. nitric acid (1.135 specific gravity), place on the hot plate, and when solution is complete. boil off all nitrous fumes. (The volume of t h e solution should not be less t h a n jj cc. It is unnecessary t o filter off t h e silicon a n d graphite residue if the solution is complete. When t h e sample is high in combined carbon, i t is well t o a d d a few crystals of ammonium persulfate when the solution is complete and boil a moment longer to dest r o y the combined carbon.) Remove the flask from t h e hot plate, add 7 5 cc. silver nitrate solution ( 2 . 0 0 g r a m s per liter), and immediately j grams of ammonium persulfate crystals. Replace flask on t h e hot plate and bring gently t o boiling. Boil vigorously for a minute, and while still boiling add dilute hydrochloric acid, drop b y drop, until the permanganate color is completely destroyed. Continue t h e boiling for one minute and then cool the flask immediately in water. Titrate by adding an excess of tenthnormal ferrous ammonium sulfate solution above t h a t required t o reduce the chromium, and titrate back with tenth-normal potassium permanganate solution. T h e number of cubic centimeters of t h e ferrous ammonium sulfate oxidized by t h e chromate, multiplied b y 0.00174, gives t h e weight of chromium in t h e sample. ceed according to the above directions for t h e determination of chromium except t h a t after the ammonium persulfate is added, only heat until t h e solution just comes t o boiling, then cool immediately and titrate as before, this time adding enough ferrous ammonium sulfate t o reduce both t h e manganese and chromium. The number of cubic centimeters of ferrous ammonium sulfate used, minus the number used in the chromium determination, multiplied b y 0.00 j j, equals the weight of manganese in t h e sample. The ultimate value of t h e solutions may be used in calculations as above. I n this case it is advisable t o carry along a blank with a sample containing no chromium and subtracting t h e blank. The standardization of the solutions against a standard steel is t h e most satisfactory procedure. There will be published shortly b y the Bureau of Standards, two papers on the subject of printing inks: one, a technologic paper on " T h e Analysis of Printing 1 Published by permission of the Director of the Bureau of Standards. Inks," and the other a circular of general information on this subject. The length of these papers is such as t o make i t unwise t o a t t e m p t t o present either of them in full a t this time, but it is desired t o give some idea of their scope. The first paper treats the subject from a n analytical point of view. Four types of ink have been investigated: web press, flat-bed, job, and half-tone inks. These included a number of colored as well as the more common black inks. The method of analysis has been in use for several years for t h e testing of supplies delivered t o the Government Printing Office, and has been found very satisfactory for this purpose. Using as the solvent a mixture of benzene and ethyl ether, the oil is separated from the pigment by means of a centrifuge. I n some cases petroleum ether m a y be used as the solvent. This method gives a n effective separation, and the pigment may be determined with a fair degree of accuracy. The oil fraction, after evaporating off the solvent, is analyzed for unsaponifiable oils (rosin and mineral oils), rosin, hard gums and linseed oil. I n t h e black inks, the pigment is ignited and t h e ash tested for driers and ferric oxide, t h e latter being the residue left on t h e ignition of Prussian blue. A qualitative test for Prussian blue is given, which will detect less t h a n one per cent of this material in the pigment. If aniline dyes are present, they may be determined by extraction b y means of alcohol, unless preliminary examination shows t h a t t h e dye is insoluble in this solvent. I n the latter event, a suitable solvent must be found. The colored inks require a preliminary examination t o determine t h e nature of t h e pigment used, and t h e method of attack depends largely upon the results of these tests. Some of t h e mineral pigments, such as vermilion (mercuric sulfide) and chrome green (i. e . , t h e material known commercially as Brunswick or Milori . Green), 'may be determined quantitatively according t o t h e procedure outlined in the original article. If t h e coloring matter consists of aniline dyes or lakes, i t will usually be found sufficient t o determine whether or not these colors are fast t o light. Two methods for this test are given. A table is given showing how closely one may expect duplicate determinations on t h e same sample t o check. These figures are t h e result of testing several hundred samples of ink b y a t least half a dozen analysts, so t h a t they may reasonably be taken as a fair mer-sure of the accuracy of t h e method. The paper also includes a brief discussion of the relation of these laboratory tests t o the practical t e s t s which may be made b y the printer. It is not the intention t h a t the latter shall be supplanted by the former, b u t t h a t the two shall supplement each other in order t o obtain t h e grade of ink which is the most suitable for t h e purpose. The second paper is the circular of information on the general subject of printing inks. It gives a brief description of some of the materials used in the manufacture of ink, and also treats broadly some of the problems concerning the relation between the ink
doi:10.1021/ie50068a013 fatcat:3tywk6whjjcobjabsdbs7rlwgm