SCIENCE. 



423 



ratus for this purpose was this dissociation accomplished 

 by heat alone. 



The reason for this state of things is apparent. Hy- 

 drogen in uniting with oxygen to form water develops 

 the greatest amount of heat, a greater amount, in fact, 

 than an equal weight of any other known element. And 

 just here 1 would ask Mr. Wallace which authority has 

 stated that the " absolute heat of carbon and hydrogen 

 are almost exactly equal in complete burning." On the 

 contrary, all authorities agree, and all investigators have 

 established beyond doubt the fact, that hydrogen devel- 

 ops more than four times as much heat on combustion 

 than does an equal weight of carbon. The figures at 

 present universally accepted as a standard are those de- 

 termined by Favre and Silberman, during their carefully 

 conducted and numerous experiments. According to 

 them — 



1 grain of hydrogen develops 34,462 units of heat. 

 1 grain of carbon " 8,080 units of heat. 



on complete combustion. 



This great advantage in the heat-producing power of 

 hydrogen is the principal reason why scientists have con- 

 stantly striven to substitute this element for carbon, 

 which is now universally used as fuel. But until lately 

 only this was thought impracticable, because it was be- 

 lieved that the same amount of heat was necessary to ob- 

 tain the hydrogen by the dissociation of water, which 

 would ultimately be obtained by the combustion of said 

 hydrogen. And even the processes of Strong and others 

 for the generation of so-called ' water-gas ' have not 

 changed this erroneous view. For, the advantages arrived 

 at by them were ascribed rather to various extraneous 

 causes* than to the one principal cause, i. e., the dissocia- 

 tion of steam by the chemical affinity of carbon, and the 

 consequent generation of a not inconsiderable amount of 

 hydrogen. 



This very same line of argument has been followed in 

 the discussions about the Holland process, and the prin- 

 cipal aim of my paper was to controvert it, and to show 

 that it is not heat, bttt chemical affinity, which does by 

 far the greatest part of the work of dissociation. I was 

 enabled to do so on the basis of Dahlerus' experiments, 

 which have proved conclusively that carbon will disso- 

 ciate water at 400 C, instead of 8000 C, which is De- 

 ville's figure for the dissociation-temperature of water in 

 the absence of any other element.! 



From the foregoing the readers of " Science " will 

 perceive that the enormous gain obtained by actual ex- 

 perii lent with the Holland locomotive is satisfactorily 

 explained on scientific grounds. 



All the further argumentation of Mr. Wallace covers 

 the earlier water-gas processes of Lowe, Strong and others; 

 they generate their gaseous fuel in a separate contrivance 

 (the generator) and afterward burn it. For this reason 

 they want to accomplish only the first stage of carbon, 

 combustion water-gas, consisting of hydrogen and car- 

 bonic oxide. In the process under consideration, however, 

 the retort which prepares the fuel, i. e., gasifies the naph- 



* Some of these are : gasification of the fuel, substitution ot the second 

 for the first stage of carbon— combustion, reduction of the amount of draft- 

 air, etc. 



t The combustion- (and dissociation-) temperature may be found by- 

 calculation from the thermal effect and the specific heat of the product 

 (z. e., water) in the following manner, according to Mohr (Mech. Theorie 

 d. chem. Affin.,p. 102) : 



If one part of hydrogen burns up with eight parts of oxygen, forming 

 nine parts of water, 34462 units of heat are generated which are contained 

 in the watery vapor thus formed. If the specific heat of steam would be the 

 same as that of water, the actual temperature of these nine parts of water 

 would be : 



— = 38290 C. 



Since the specific heat of steam is, however: .475, the actual tem- 

 perature of the nine parts of watery vapor is : 



2^= 8o6x<> C. 



-47S j .... 



For this reason 8000 C has been assumed as the dissociation-tempera- 

 ture of watery vapor. 



that and the water, is placed just where the heating is to 

 take place. All the heat, therefore, that is developed by 

 the carbon combustion is utilized, as is also all the heat 

 which is developed by the dissociated hydrogen burning 

 up with atmospheric oxygen. 



Indeed, this process is the only one which comes pretty 

 near to fulfill all the requirements of an ideal method. 

 These are ; 



1. Gaseous condition of the fuel. 



2. Complete combustion (no smoke, no ashes). 



3. Full effects of the caloric energy developed. 



4. Regulation of the draught-air, so as to admit the 

 least amount of atmospheric air practicable. 



5. Greatest possible percentage of oxygen in atmos- 

 phere of combustion. (The oxygen derived from the dis- 

 sociation of the steam being employed for the combustion 

 of carbon, the necessary draught-air is thereby materially 

 reduced and thus the percentage of oxygen increased). 



6. Universal adaptibility (kitchen and parlor stoves, fire 

 places, stationary and other boilers, locomotives and ocean 

 steamers can be accommodated with it, and illuminating gas 

 is prepared automatically by an additional chamber in the 

 retort). 



7. Simplicity of apparatus. (May be managed by the 

 turning of a few faucets.) 



8. Cheapness of the fuel employed. (Water is certainly 

 to be obtained everywhere at small expense, while the 

 price of naphtha is only three cents a gallon if bought by 

 the single barrel.) 



9. Fuel used of the greatest heating capacity, with 

 each atom of Carbon burned, there are burned at the 

 same time four atoms of Hydrogen, thus : 



C 2 H„ + 



(Naphtha.) 



4 HO = 2 (CO.,) 

 (Water.) 8 H. 



The eight Hydrogen are burned with atmospheric 

 Oxygen. 



Crude oil i. e. petroleum that has undergone one distil- 

 lation, to free it from its mineral and waxy ingredients, 

 may be used, but would be much dearer. Naphtha, it 

 may be said in conclusion, is not one of the distillation 

 products, as might be inferred from the name : It is the 

 unused residue from all the various distillation-processes 

 to which petroleum is subjected. // is a waste product 

 and therefore cheaper than anything else. 



It is obtained in this wise : 



The crude oil as it is received from the stills of the 

 petroleum regions is subjected to twelve successive 

 distillations, and the following products result : 



Cymogene. 



Rhigolene. 



Gasolene. 



C. Naphtha. 



B. Naphtha. 



A. Naphtha. 



Benzine. 



Kerosene. 



Mineral Sperm Oil. 



Lubricating Oil. 



Paraffin. 



Of these only the last four are completely used in the 

 arts and for illuminating purposes. The unused residue 

 of all the others is thrown back into the residue remain- 

 ing from the last distillation. The quality of the mixture 

 called Naphtha, and used in the Holland process is there- 

 fore not always the same, but this does not at all alter its 

 value as a fuel, as it does not alter the main features of 

 this process, as they have been explained in our remarks. 



Geo. W. Rachel, M. D. 



