16 



SCIENCE 



[N. S. Vol. LIV. No. 1383 



Lycopsida 



Order 1. Lyeopodiales 

 2. Equisetales 

 Pteropsida 



Class 1. Aspermse (Ferns) 



2. GymnospemiEe 



3. AngiospermEe 

 Subclass 1. Dicotyledonese 



Ddvision 1. ArchichlamydeEe 

 Order 1. Oasuarinales 

 Family 1. CasuarinacesB 



Division 2. Mefcachlamydese 

 Subclass 2. Monocotyledonese 

 Order 41. Pandanales 



51. Orcbidales 

 Family 284. Orohidacese 



Henry S. Conard 

 Grinnell, Iowa, 

 May 16, 1919 



THE AMERICAN CHEMICAL SOCIETY 



(Continued) 

 Studies in fluoride equilibria: I. Calcium boro- 

 fluoride: A. F. 0. Germann and Gilberta Tok- 

 KET. Moissan, in his work with boron trifluoride, 

 passed the gas through a tube containing heated 

 calcium tluoride, presumably to free the gas from 

 any hydrogen fluoride that might contaminate it. 

 Calcium borofluoride, Ca(BF4)2 is described in the 

 literature, and it seemed reasonable to expect the 

 formation of a similar compound under the con- 

 ditions of Moissan 's work. To determine this, 

 weighed samples of calcium fluoride were heated 

 for several days at a temperature of 200° C. in 

 an atmosphere of pure boron trifluoride under a 

 pressure of 430 mm. Absorption took place slowly, 

 and until one half molecule of the gas was 

 absorbed. Blanks were run to determine the 

 amount of absorption by the glass, etc., of the 

 reaction tube; this absorption was found to be 

 slight. The compound, 2CaF„.BF3, forms by di- 

 rect union of the constituent molecules under the 

 conditions outlined. 



Chromatic emulsions: Harrt N. Holmes and 

 Donald H. Cameron. A "solution" of ordinary 

 cellulose nitrate (11 per cent, nitrogen) may be 

 somewhat diluted with benzene and then emulsi- 

 fied with glycerol. A creamy white emulsion of 

 drops of glycerol in the other liquid results. With 

 addition of enough benzene the indices of refrac- 

 tion of the two liquids may be made equal, thus 



securing a transparent emulsion. With the right 

 amount of benzene a very beautiful yellow emul- 

 sion which is a soft blue by transmitted light is 

 produced. The next step up in the "color chro- 

 matic scale" is a pink emulsion which transmits 

 green light. Next a lavendar emulsion is made 

 transmitting yellow light. With still more ben- 

 zene a blue-green emulsion is secured with a sun- 

 set red glow by transmitted light. The colors are 

 explained by the great difference in dispersive 

 power of the two liquid phases, transparency 

 being fundamentally necessary to let the light 

 through. 



Cellulose nitrate as an emulsifying agent: 

 Harry N. Holmes and Don H. Cameron. By the 

 use of cellulose nitrate as an emulsifying agent 

 emulsions of the ' ' water-in-oil ' ' type may be pre- 

 pared. Cellulose esters containing about 11 per 

 cent, nitrogen are most suitable. "Water-in-oil" 

 emulsions are far less stable than the more usual 

 ' ' oil-in-water ' ' type. To prepare the former such 

 emulsifying agents as calcium and magnesium 

 soaps, lanolin, carbon and rosin have been used. 

 However, cellulose nitrate is far superior to these 

 agents in the stability of the emulsions produced 

 by its aid. For example, if water be shaken with 

 a suspension of cellulose nitrate in amyl acetate 

 (2 per cent, is suitable) a good white emulsion of 

 drops of water dispersed in amyl acetate is ob- 

 tained. Instead of amyl acetate any liquid that 

 peptizes ("dissolves") the cellulose ester may 

 be used provided also the two liquids are im- 

 miscible. One of the important factors in the 

 formation of this emulsion is the formation of a 

 tangible film around each drop. With a very 

 large drop the film may be observed under suitable 

 conditions. It is probably formed by great ad- 

 sorption, to the point of coagulation of the cel- 

 lulose nitrate at the liquid interface. 



A theory of the photographic latent image: 

 Harris D. Hineline. The suggested theory con- 

 cerns itself with the latent image as distinct from 

 the photo-electric effect on the silver halide, and 

 as distinct from the print out image. A reaction 

 between the dissociation products of the silver 

 halide and gelatine which will yield energy enough 

 to account for the energy discrepancy pointed out 

 by other workers, is suggested. In terms of this 

 theory the latent image then consists of a combina- 

 tion between the bromine and substituted am- 

 monia of the gelatine and the silver and amido 

 acid, the amido acid compound being much more 

 easily reducible than the bromine compound of 



