August 7, 1914] 



SCIENCE 



191 



sate for their more expensive equipment 

 and operation. Moreover, there are some 

 purposes where the initial caustic solution 

 of rather high concentration, produced 

 directly in these cells, can be used as it 

 is without further treatment, thus obviat- 

 ing further concentration and cost of fuel. 



The expenses for evaporation and elimi- 

 nation of salt from the raw caustic solu- 

 tions increase to an exaggerated extent 

 with some types of diaphragm cells, which 

 produce only very weak caustic liquors. This 

 is also the case with the so-called "gravity 

 cell," sometimes called the "bell type," or 

 "Aussig type," of cell. But these gravity 

 cells have the merit of dispensing with 

 the delicate and expensive problem of dia- 

 phragms. On the other hand, their units 

 are very small, and, on this account, they 

 necessitate a rather complicated installa- 

 tion, occupying an unusually large floor 

 space and expensive buildings. 



The general tendency is now toward cells 

 which can be used in very large units, 

 which can be housed economically, and of 

 which the general cost of maintenance and 

 renewal is small; some of the modern 

 types of diaphragm cells are now success- 

 fully operating with 3,000 to 5,000 amperes 

 per cell. 



As to the possible future improvements 

 in electrolytic alkali cells, we should men- 

 tion that in some types the current efficien- 

 cies have practically reached their maxi- 

 mum, and average ampere efficiencies as 

 high as 95 to 97 per cent, have been ob- 

 tained in continuous practise. The main 

 difficulty is to reinforce these favorable 

 results by the use of lower voltage, without 

 making the units unnecessarily bulky, or 

 expensive in construction, or in mainte- 

 nance, all factors which soon outweigh any 

 intended saving of electric current. 



Here, more than in any other branch of 

 chemical engineering, it is easy enough to 



determine how "good" a cell is on a 

 limited trial, but it takes expensive, long 

 continuous use on a full commercial scale, 

 running uninterruptedly day and night 

 for years, to find out how "bad" it is for 

 real commercial practise. 



In relation to the electrolytic alkali in- 

 dustry, a great mistake is frequently com- 

 mitted by considering the question of 

 power as paramount; true enough, cheap 

 power is very important, almost essential, 

 but certainly it is not everything. There 

 have been cases where it was found much 

 cheaper in the end to pay almost double for 

 electric current in a certain locality, than 

 in another site not far distant from the 

 first, for the simple reason that the cheaper 

 power supply was hampered by frequent 

 interruptions and expensive disturbances, 

 which more than offset any possible saving 

 in cost of power. 



In further corroboration, it is well known 

 that some of the most successful electro- 

 lytic soda manufacturers have found it 

 to their advantage to sacrifice power by 

 running their cells at decidedly higher 

 voltage than is strictly necessary — which 

 simply means consuming more power — and 

 this in order to be able to use higher cur- 

 rent densities, thereby increasing consid- 

 erably the output of the same size units, 

 and thus economizing on the general cost 

 of plant operation. Here is one of the 

 ever recurring instances in chemical manu- 

 facturing where it becomes more advan- 

 tageous to sacrifice apparent theoretical 

 efficiency in favor of industrial expediency. 



AU this does not diminish the fact that 

 the larger electrochemical industries can 

 only thrive where cheap power is available. 



Modern progress of electrical engineer- 

 ing has given us the means to utilize so- 

 called natural powers; until now, however, 

 we have only availed ourselves of the 

 water-power developed from rivers, lakes 



