118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. DISCUSSION 61 I Dr. J. N. Pring said he took it that the treatment of this charcoal with aqua regia was less drastic than with nitric acid alone, because as far as he could remember amorphous carbon was very rapidly decomposed by nitric acid.Was it the hct that aqua regia wasless drastic? Dr. J. B. Firth said that if it were too hot, the bulk of the carbon was lost by decomposition. If the charcoal were treated with strong nitric acid alone there was a tendency to lose a lot of the carbon, whereas by treating the charcoal with aqua regia they were treating it with an active form of chlorine. If it were too hot, however, the solution became dark brown and a lot of carbon was lost. Dr. Pring said that in purifying cocoa nut charcoal he always used chlorine gas at a high temperature followed by heating in hydrogen. In that way it was possible to eliminate the hydrocarbons and some ash with- out decomposing the carbon. Had the author attempted a treatment of that kind with aqua regia? Dr. Firth said he had tried to approximate to that, by heating up until a fairly heavy stream of chlorine was given off, but he did not allow the temperature to rise any higher, otherwise the whole of the carbon passed into solution, and a brown viscous residue was obtained.Dr. H. Borns asked of what the 6 per cent. residue consisted? Dr. Firth said it was almost entirely iron ; there was a slight trace of Dr. Borns: And you cannot get rid of that by means of bromine? Dr. Firth said not without very prolonged treatment was he able to reduce it to any extent greater than was indicated by the figures in the paper. I t was necessary not to make the treatment too drastic because the activity of the carbon would be altered by an alteration in the treatment and he wished to keep as far as possible to a uniform treatment and in- vestigate the effect of the impurity by other methods.Dr. R. Lessing said he was interested in conclusion No. 4 of the Summary to the paper dealing with the effect of the iron in the charcoal on the activation, which the author regarded as a kind of spacing action of the iron. In some work which he did some years ago-and in which he was again engaged-he found that the addition of inorganic substances to carbonaceous products of various kinds had what he believed to be a catalytic influence on the carbonisation. Therefore in the present case, when iron oxide or hydroxide was added to the sugar solution, one would expect an entirely different form of physical structure with carbon than one would get with iron. How iron or any other inorganic agent would act we did not know but he would like to throw out one suggestion for the authors’ consideration, and that was that although he did not find any action to speak of with the ashes or with iron reduced by coal gas, or reduced pure iron, it was not unlikely that the iron in the charcoal itself acted quite differently from the isolated iron.Particularly where one was dealing with ashes it was necessary to consider the question of sintering which depended very much on the temperature at which the ash was prepared and also on the gas with which the ash or iron were reduced; hydrogen, coal gas or whatever it may be. In the case of coal gas one has to guard against small traces of sulphur, although they did not come out in the figures in the paper as being of a poisonous nature.Certainly the iron in the charcoal might act quite differently and it might be of an entirely different physical silica but the bulk of it was iron.612 DECOMPOSITION OF HYDROGEN PEROXIDE condition; further, the nature of the reduction would be a different one. In the one case the reduction was presumably by solid carbon, with the formation of CO, whereas in the other case we had to deal with hydrogen reduction. Whether or not we had to deal with a uni-molecular layer of iron and carbon he did not know, but any way it would be quite on the cards that the iron would be in an entirely different form from that in other cases. The President said he took it that the authors assumed that the iron formed a kind of network throughout the carbonaceous mass, breaking it up and so gradually increasing the surface for action.If that be so, it would be interesting to try by some other manner entirely different from the one they had used, such as, perhaps, by taking a radiograph, to see if the iron were scattered through the mass in gross particles, or if there were a network. Dr. E. Fyleman pointed out that if charcoal is heated with iron oxide at gooo C., there will surely be considerable oxidation, and this would con- siderably increase the surface extension of the mass which would presum- ably increase the activity. I t seemed to him that a very large proportion of the results in the paper could be interpreted on these lines. Oxidation of part of the charcoal would account for the decrease in the weight of the the charcoal that the author obtained. There was another rather interest- ing analogy.If pure charcoal was treated with liquid oxygen, nothing happened, unless, of course, the mixture were detonated. If, however, they had charcoal containing more than a certain proportion of iron, they were very likely to obtain a violent explosion. Dr. Firth, replying to the discussion, said that with regard to breaking up and offering more surface, in the previous experiments of the authors with carbohydrate carbons it was shown that the actual bulk of the carbon is not as decisive a factor as was imagined. In the carbohydrate carbons the volume occupied by one gramme of finely divided carbon in the case of cellulose was 3.9 C.C. ; cellulose was exceedingly active relative to the other carbohydrates.In the case of carbon prepared from rice starch, one gramme of that charcoal occupied 6 c.c., and yet the one with the smaller volume was by far the more active. They had measured the bulk density of these carbons and there seemed to be no direct relation between the bulk density, which one could take approximately as a measure of the surface, and the activity. Their idea with regard to the action of iron was that the presence of iron in any carbonaceous substance distributes itself and prevents the formation of highly complex carbon molecules. I t was the simplest carbon molecules which possessed the high activity and they were more or less unstable, and that was one reason why the activity of the charcoal decays.It is shown in the paper that a certain amount of residue occupies 0.4 C.C. in the ash, whereas the same amount of ash is distributed through 4 C.C. in the actual carbon. We appreciate the remarks of Dr. Lessing and indicate in our paper that it is possible that the iron when distributed throughout the charcoal behaves differently from the iron in the ash or the reduced iron itself. On the other hand from our investigations with charcoals containing impurities other than iron, similar results have been obtained, that is, whilst the impurity, either as the substance itself or as the ash from the charcoal exhibits relatively small activity, it produces a considerable increase in the activity of the charcoal. Hence it would appear that the explanation, in the main, must be of a general character, and not necessarily a specific property of any particular impurity.DISCUSSION With regard to some later experiments which were not included in the paper, and which we do not wish published at present, we have investigated a commercial charcoal which it has been possible to activate to an activity which approximates to chemical decomposition.We took 0.1 25 gramme carbon in 12.5 C.C. of peroxide and got over go per cent. of the-available oxygen off in the first half minute, and the reaction was practically complete in three minutes. That carbon contained very little iron; the chief im- purity was phosphate. We have been investigating recently another carbon which possessed very great activity with regard to the absorption of colour- ing matter in solutions of iodine and sugar solutions, and although it was very highly active under these conditions, it showed, up to the present, very feeble activity with regard to decomposition of hydrogen peroxide. I t showed no alpha activity; it was only a slight activity, going on for about several hours. Therefore, this would indicate that there is no direct connection between sorption activity and catalytic activity, as we were inclined to believe in the first place.