atoms is 0.99. For this to be true, the found by adsorption is therefore the true platinum must be present either in “islandsyJ one, the difference becoming progressively of only one atom thickness, or in three- less as the number of small particles decreases. dimensional crystallites whose sides are less The effect of carbon deposition and re- than two unit cells in length (I). Similar moval on particle size was also studied: conclusions are drawn by the other group of carbon was deposited by causing the catalyst workers. The effect of heat treatment on the to operate in a reforming reactor. A one-day particle size was also investigated, and ‘(coking” reduces the hydrogen adsorption of some of the results are summarised in the a catalyst by almost five times, even although table. The first three entries and the last sufficient carbon is present to cover only two separately show that continued sintering 5 per cent of the total catalyst surface. gives progressively better agreement between Carbon deposition must therefore occur the two methods of determination. The principally on the metal. Regeneration was interpretation of this, given in similar terms effected by heating in a muffle-furnace, and by both groups, is that after a little sintering if this was done below 600°C little loss in some of the platinum has grown to form large hydrogen adsorption took place. crystallites (recorded by line-broadening), These papers have established the useful- while much of the platinum remains as small ness of measurements of hydrogen adsorption crystallites (undetected by line-broadening). in the determination of the size of the This distribution of crystallite sizes is elementary metal crystallites present in described as bimodal. The mean diameter supported catalysts. C. C. B.
References
I L. Spenadel and M. Boudart . . . . Dispersion of Platinum on Supported Catalysts, 3.Phys. Chem., 1960, 64, (z),204-207 2 S. F. Adler and J. J. Keavney . . The Physical Nature of Supported Platinum, J. Phys. Chem., 1960, 64, (z),208--212
Ruthenium, Rhodium and Iridium in Catalysis A SYSTEMATIC SURVEY OF THE LITERATURE
The literature on both platinum and Bebbington of the company’s Development palladium as catalysts is very extensive, and and Research Division, the bibliography con- these two metals are widely employed in a tains more than three hundred abstracts of variety of reactions on a commercial scale. papers and patent specifications, covering The catalytic properties of the other members the period from 1881 to mid-1959. They are of the platinum group of metals are by no arranged in sections dealing respectively with means so fully appreciated, nor are they the hydrogenation of organic compounds, employed for this purpose to anything like other reactions of organic compounds, re- the same extent. But scattered throughout actions with inorganic compounds, and the world’s scientific literature are quite a catalyst properties. number of records of research carried out The variety of catalytic reactions for which with one or other of these metals as catalysts these metals have been investigated is ex- in many different types of reactions. tremely wide, and the collection of this An admirable survey of this literature has considerable amount of data into one carefully now been prepared and published by the arranged volume will unquestionably provide International Nickel Company Inc., New a most useful source of information for York, as an Annotated Bibliography on Ruth- chemists and chemical engineers concerned enium, Rhodium and Iridium as Catalysts. with reactions in which one or other of these Compiled by Ann E. Rea and Marguerite metals may provide the most suitable catalyst.
Platinum Metals Rev., 1960, 4, (3) 93