MATHEMATICS AND NATURAL PHILOSOPHY. 195 



the chlorides of bismuth and arsenic instead of the chloride of phosphorus. The 



following are the formulae of the compounds as yet examined : 

 P (C 2 H 3 ) 3 P (0 4 H 5 ) 3 (C» H 3 ), I 



P (O Hs) 3 P (C* H«) *, I 



P (C 10 H") 3 , P (C* H 5 )3, (C I0 H»), I 



P (C» H 3 ) 3 (C 4 H*), I P (GM> H") 3 (C 2 H 3 ), I 



P (C 2 H 3 ) 3 (C"> H 11 ), I P (C'° H") 3 (c* H»), I 



P (C 1 " Hn) *, I 



SAPONIFICATION. 



It was already known that fats and oils could be decomposed into glycerine and 

 their respective acids, both by the action of a very small quantity of bases and by 

 the influence of water or its vapour at a high temperature, and this plan has already 

 been adopted in some large candle factories. Pelouze has shewn that the same 

 can be effected by the action of soaps on fatty matters at a temperature corres- 

 ponding to the pressure of five or six atmospheres. He supposes that the hi^h 

 temperature decomposes the neutral soap into a very basic one, which then acts on 

 the fatty matters in the same manner as a free alkali. 



TESTING ACETIC ACID. 



Nicholson and Price have shewn that the method of determining the strength of 

 acetic acid by means of carbonate of soda is open to objection, owing to the alka- 

 line reaction of the resulting acetate. The methods with carbonate of lime or 

 baryta, or the process of Fresenius and Will are to be preferred as giving accurate 

 results. H. C. 



MATHEMATICS AND NATURAL PHILOSOPHY. 



PHOTOGRAPHY. 



M. TaiipenoVs Process. — The following information with regard to this process 

 is condensed from M. Taupenot's paper, which appeared originally in La Lumiere 

 and a translation of which was given in the Journal of the Photographic Society 

 for September last ; and also from a translation in the October number of the 

 latter Journal, of an article in the Bulletin de la Societe Fran$aise de la Photo- 

 graphic This new method of M. Taupenot is a combination of the collodion and 

 albumen processes ; and it promises to be very useful, because the plates may be 

 used dry, and apparently some time after they have been excited, while their 

 sensibility is nearly as great as that of ordinary collodion plates. 



M. Taupenot's process is briefly as follows : — 



I. Coat the glass plate with iodized collodion in the ordinary manner, place it 

 as usual in the nitrate bath, and then wash the surface with distilled water. 



II. LTpc-n the plate thus coated with collodion pour a sufficient portion of 

 iodized albumen, pour off the excess, and set the plate up against the wall to 

 drain. 



III. To sensitize the plate plunge it into a bath of aceto-nitrate of silver, cod. 

 sisting of 48 grains of nitrate of silver, and about 44 minims of glacial acetic-acid 

 to the ounce of distilled water. 



IV. After exposure develope either with gallo-oitrate, (which seems, however, 

 a very slow operatioD), or with pyro-gallic acid, with a heavy dose of acetic acid 

 adding a small quantity of the aceto-nitrate. 



