Expressions are derived which predict satisfactorily the observed isomer and carbon number distribution of products from iron and cobalt catalysts in the Fischer-Tropsch synthesis. These expressions are based on three schemes of stepwise addition of one carbon atom to the end or adjacent-to-end carbons of the longest carbon chain of the growing group at the catalyst surface. The implications of these schemes to some general aspects of the reaction mechanism are considered.

No abstract

INDUSTRIAL AND ENGINEERING CHEMISTRY 991 or compensated for, when substituting reclaim for rubber, by taking diluents or excess filler from the rubber stock and by adding reenforcing material to the reclaim stock. They failed to realize that the same measures which would improve the reclaim tread could be applied to the base stock.If it were true that, due to the plasticizing effect of the reclaim, it would be possible to carry higher black loading in the reclaim tread stock with the same ease of handling, there would be some weight to the argument that the reclaim can be compensated for by adding black. Factory practice does not show this to be the case. On the contrary, the added black must be considerably reduced to keep the same handling conditions. If it were possible to process the reclaim stock with higher black, then it would also be possible to add more black to the non-reclaim stock and keep the differential in road wear.Since this is the case, if the non-reclaim tread stock is taken with no diluent or excess zinc oxide and with as much black loading as can be processed, then it is not possible to make compensation for the effect of the reclaim. These facts were put forth very clearly by Cranor (ß), who states that "A better tread can be made without reclaim than can possibly be made with it."The series in the present paper was not designed primarily to show the extent to which wear will fall off with the use of reclaim in a series of practical tread stocks. However, since no compensation for its effect is possible, the wear in such a series would fall off even faster than in the series in this paper, for in the latter diluent materials were added to the non-reclaim stock. Therefore, it can be said that up to 20 per cent, the use of reclaim will cut down the resistance to road wear by approximately the percentage used. This is essentially the conclusion reached by Holt and Wormeley (3). Their method was severely criticized by Bierer and Davis, but considering that their base stock was as stiff and tough as was considered practical at the time, this criticism was not justified and their conclusions were essentially in line with the facts. AcknowledgmentThe writer -wishes to express his appreciation to W.W. Vogt for valuable suggestions and criticism.

No abstract

No abstract