322 



SCIENCE. 



carbon of the Naptha-gas reduces the dissociation-tem- 

 perature. 



The fact that under certain conditions carbon has a 

 dissociating action on steam, or — as some put it — carbon 

 may be burned up with watery-vapor, has been known 

 for a long time ; the presence oi free hydrogen in furnace 

 and generator-gases is due to this circumstance. The 

 difference between the dissociating action of carbon on 

 water-vapor as compared with that of the metals above- 

 mentioned is only one of degree. The temperature at 

 which it takes place is much tower. 



After a prolonged and careful observation of the phe- 

 nomena connected with the Naphtha and water-process 

 under consideration, the writer was firmly convinced that 

 the carbon in them plays the role of a dissociating agent, 

 and that the temperature at which its dissociating prop- 

 erty asserts itself must be a low one, comparatively speak- 

 ing. For, in this way only was it possible to account for 

 remarkable results of the Holland heating method. 



Unhappily, we were not then acquainted with the ex- 

 periments presently to be discussed, although the fact 

 privately communicated to us that Mr. Moses Farmer, 

 of Hartford, the well-known philosopher, had found ex- 

 perimentally the temperature at which carbon will disso- 

 ciate water-vapor to be not much above 900 C, seemed 

 to confirm the position taken. 



While our proposal to entrust some able chemist with 

 this investigation was under consideration, we became 

 aware of the fact that the desired experiments had al- 

 ready been made in another quarter of the globe more 

 than a year ago. Thus, fortunately, a doubt of their 

 genuineness, which otherwise might perhaps have been 

 entertained by the opponents of the Holland method, 

 is out of the question. 



Professor Ackerman, who is superintendent of the 

 chemical labratory at the Stockholm School of Mines, re- 

 quested one of his assistants, Mr. C. G. Dahlerus, to 

 make some experiments with the view of determining the 

 temperature and other circumstances required for the 

 combustion of carbon with watery vapor. The real aim 

 was to explain the occurrence of free hydrogen In both 

 furnace and generator gases ; this fact is, as we said be- 

 fore, well-known to mining engineers. 



The apparatus used by Dahlerus consisted of a tube 

 filled with charcoal, which was heated in a combustion 

 furnace, while steam, generated in a separate boiler, was 

 allowed to pass through it. The temperature was deter- 

 mined by trays of steatite containing pieces of Mayer- 

 hofer alloys, with various melting points being intro- 

 duced into the tube. The gases generated were collected, 

 after having passed through a spiral gas tube in order to 

 condense the steam they contained, and were then anal- 

 yzed. Every experiment lasted at least two hours before 

 a sample of the gas was taken, the pressure of the steam 

 in the induct pipe being kept as uniform as possible. 



The results of these experiments have confirmed the 

 correctness of our position, and have shown that dissocia- 

 tion of watery vapor in the presence of carbon takes place at 

 much lower temperatures than has hitherto been admitted. 



Mr. Dahlerus, in giving a table of his results, sums 

 up as follows : 



" On examining this table it appears that watery vapor 

 is decomposed at a temperature which is indicated by the 

 alloys as from 450 to 500 C; but the temperature may, 

 in fact, not have been higher than 400 C, because zinc 

 in the interior of the tube was not fused in any of the 

 first five experiments." 



It is evident that in the Naphtha and water process 

 the conditions, under which the dissociating action of 

 carbon on water vapor takes place, are much more favor- 

 able to it than those obtained in the apparatus used by 

 DALHERUS for his experiments. 



In the first place the action of carbon in the latter 

 gentleman's apparatus could not but be of a very slow 

 nature, the surface only of the glowing charcoal in the 



tube being enabled to gasify and act chemically on the 

 steam surrounding the pieces of it. In the process un- 

 der consideration, however, the whole of the carbon 

 of the naphtha is in gaseous condition and by diffusion 

 the vapor is acted upon simultaneously at every point. 

 Furthermore, this very gasification of the carbon re- 

 quires a definite, not inconsiderable, amount of heat 

 which in Dahlerus' apparatus has to be supplied by 

 the steam itself, this being the only substance admitted 

 into the presence of the charcoal in the tube. In the 

 new process, on the contrary, this gasification is effected 

 before the carbon-compounds of the naphtha are mingled 

 with the steam and no loss is therefore expeiienced in 

 in this direction. But, aside from these details — for the 

 combustion-furnace will probably furnish the wanting 

 heat — the highly important fact is established by these 

 experiments that chemical affinity does, in this dissoc'a- 

 tion process, supplant heat for the greater part. And, 

 considering the great advantages, above detailed, of the 

 Holland process over these experiments, we are justi- 

 fied in assuming the lowest temperature, found sufficient 

 by Dahlerus in five of his experiments, as entirely 

 sufficient in the Holland process also. Instead of 

 fc'000 C, therefore being required for the dissociation of 

 water, it will here take place at 400 C. 



A gain therefore of, say for convenience's sake, nine- 

 teen twentieths is effected ; for every particle of hydrogen 

 thus dissociated and liberated, at 400 C, will develope 

 its full 8000 ^ C, on combustion with oxygen, i. e., on be- 

 ing burned up by the draft air. And this saving is ac- 

 complished by the supplanting of heat with chemical 

 affinity, the latter performing the greatest part of the 

 work of dissociation. 



Nor is this all ! 



It is necessary to state here that Dahlerus in pur- 

 suing his work had in view also, the preparation of 

 water gas, which has been introduced into Sweden by 

 Prof. Torrel, who was one of the commissioners from 

 that country to the Centennial Exhibition at Philadelphia. 

 He therefore endeavored to find the most favorable con- 

 dition for the production of water gas, a mixture of 

 hydrogen and carbonic oxide which is known in this coun- 

 try under various names (e.g. Strong, Lowe and others.) 



This explains the following sentence in the conclusions 

 he draws from his results : 



" Further we see that the greater the excess of watery 

 vapor the richer in carbonic acid are the gases ; or, in 

 other words, that carbonic oxide is very easily burned to 

 carbonic acid by means of watery vapor, and that the 

 content of carbonic oxide is increased both by a lessened 

 excess of watery vapor and by the raising of the temper- 

 ature. The best gas is thus obtained by raising the 

 temperature as high as possible and by a moderate supply 

 of steam." 



What Dahlerus refers to as the best gas must be un- 

 derstood to he. water gas in the accepted sense of the 

 word, viz. : A mixture of carbonic oxide with hydrogen. 

 It is for this reason that he advises the use of a limited 

 supply of steam only ; for, if there is an unlimited supply 

 of steam, the dissociation of the same continues and the 

 carbon, instead of being confined to its first stage of ox- 

 idation (to carbonic oxide), completes this process and is 

 burned up to carbonic acid. Although the result is by 

 these means a gas much richer in hydrogen — in fact 

 twice as rich — this is not what the manufacturer of 

 water-gas wants. He wants a product that may be used 

 for illumination as well as for heating purposes and, 

 therefore, he does not want an almost pure hydrogen- 

 flame — which is non-luminous, as is well known. But 

 with the Holland process this is quite different ; here 

 the manufacture of illuminating gas is effected in a sepa- 

 rate automatic arrangement which does not concern us 

 here now. In the process under consideration, therefore, 

 the heating quality of the gases is the only consideration. 

 This, the mere so, since there is here no separate gener- 



