September 9, 1921] 



SCIENCE 



227 



advantages and limitations of tiese machines. (4) 

 Efficiency is dependent upon the physical charac- 

 teristics of the material to be handled, the initial 

 and final moisture contents, the kind of fuel em- 

 ployed and the method of application of the dry- 

 ing medium. (5) When use of waste heat from 

 other processes is advisable and economical. 



Tunnel dryers: Grahame B. Eidlet. For the 

 purposes of this paper, tunnel dryers are limited 

 to those having material on trays which are moved 

 progressively through a tunnel which is supplied 

 with a current of heated air from which all the 

 heat used for drying is obtained and by which all 

 the moisture is removed. Details of their opera- 

 tion were described. 



The spray process: E. S. Fleming. 



Vacuum drying: Chas. O. Lavett and D. 

 J. Van Maele. The paper gave an outline of the 

 principles of vacuum drying, in particular the heat 

 transmission and the influence of the vacuum on 

 the temperature and rate of evaporation. A more 

 detailed description was given of the vacuum shelf, 

 rotary and drum dryer, their construction, applica- 

 tion and cost of operation. 



Tests on counter-current Tcelp driers: G. C. 

 Spencer and E. B. Smith. Details were given of 

 tests made at the kelp-potash plant of the TJ. S. 

 Bureau of Soils at Summerland, Calif., during the 

 year 1918. 



The preparation, properties and constitution of 

 liquid and solid water-glasses: Louis Schneider. 

 Liquid water-glass may be prepared by a number 

 of methods, of which the furnace process is at 

 present the most widely employed in this country. 

 Solid water-glass may be produced by dehydration, 

 hydration, synthetic and crystallization methods. 

 A practical crystallization method is unfortunately 

 limited to the meta-silicate ratio. A continuous 

 dehydration method at atmospheric pressure offers 

 the best means of attaining a stable and completely 

 soluble water-glass at a low cost. A number of 

 important properties of liquid and solid water- 

 glasses, as well as of sodium meta-silicate crystals 

 and silicic acid hydrogels, have been fully de- 

 scribed. It has been shown that solution and not 

 dilution occurs when a solid water-glass is mixed 

 with water. Viscosity is mainly a function of the 

 sodium meta-silicate content. The free causticity 

 of concentrated liquid water-glasses may be ascer- 

 tained by the attainment of the heat of solution of 

 a hydrated silica in the concentrated liquid water- 

 glass and in a dilute caustic soda solution. It 



has been established {a) that a liquid water-glass 

 is primarily a solution of sodium meta-silicate, 

 silicic acid and, if the maximum solubility of the 

 latter is exceeded, silicic acid hydrogel; and (6) 

 that a solid water-glass, above the ratio of 

 1 Na.0 : ISiOa, is a mixture of hydrated sodium 

 meta-silicate and an incompletely dehydrated silicic 

 acid hydrogel. A system of nomenclature has been 

 proposed to eliminate the prevalent indefiniteness 

 of the terms employed in the literature and the 

 trade. 



Method for treating filter oalce obtained in re- 

 fining vegetable and animal oils : Charles Basker- 

 viLLE. According to the Baskerville process, vege- 

 table and animal oils are refined by treating with 

 caustic, a determined amount of cellulose such as 

 paper pulp or "linters" being mixed in with the 

 oil, and heating to a "break." The soap par- 

 ticles are hardened and colloids are agglomerated 

 by the further addition of anhydrous sodium sul- 

 phate or sodium carbonate. The insoluble mass 

 thus produced is filtered out. The filter cake ob- 

 tained may be subjected to squeezing in another 

 press whereby some whole oil is recovered and a 

 more compact cake results. The author also de- 

 vised a process for recovering the remaining whole 

 oil and the fatty acids in the cake. It depends 

 upon cooking up the cake with an acid solution 

 and running the completely disintegrated acid 

 mass, the linters or paper pulp forming a filtering 

 medium, which makes a complete separation of the 

 hot mixture of free fatty acids and water solu- 

 tions of salts and acids from the fiber. The free 

 fatty acids and the whole oils rise to the top of the 

 mixture and may be separated by any of several 

 well-known methods, washed with hot water, the 

 product being thus converted into a soap making 

 material containing approximately fifty per cent, 

 free fatty acids and fifty per cent, whole oil. 

 A patent covering the process has been applied 

 for. 



The application of the Cottrell precipitator to the 

 wood distillation process: L. F. Hawlet and H. 

 M. Pier. Eece.nt experiments on a wood distilla- 

 tion retort holding about 75 pounds of wood have 

 shown that the Cottrell precipitator can remove 

 from the vapors coming from the retort practically 

 all of the tar. The pitch formed during the dis- 

 tillation of the wood is non-volatile and is carried 

 over to the condenser in the form of a fog of 

 fine particles. If the precipitator is kept at too 

 high temperature the pitch precipitated is so hard 

 that it builds up across the tubes and causes short 



