288 On an Improvement in the daguerreotype Process. 



was successful, and find that bromine, chloride of iodine and 

 iodine, may be united with lime, forming compounds having 

 properties similar to the so-called chloride of lime. 



The bromide of lime* may be produced by allowing bro- 

 mine vapour to act upon hydrate of lime for some hours: the 

 most convenient method of doing this is to place some of the 

 hydrate at the bottom of a flask, and then put some bromine 

 into a glass capsule supported a little above the lime. As heat 

 is developed during the combination, it is better to place the 

 lower part of the flask in water at the temperature of about 50° 

 F. : the lime gradually assumes a beautiful scarlet colour, and 

 acquires an appearance very similar to that of the red iodide 

 of mercury. The chloro-iodide of lime may be formed in the 

 same manner : it has a deep brown colour. Both these com- 

 pounds, when the vapour arising from them is not too intense, 

 have an odour analogous to that of bleaching powder, and 

 quite distinguishable from chlorine, bromine or iodine alone. 



Those Daguerreotypists who use chlorine in combination 

 with bromine, as in Wolcott's American mixture, or M. Gue- 

 rin's Hungarian solution, which is a compound of bromine, 

 chlorine and iodine, may obtain similar substances in the solid 

 state, which may be used with great advantage. By passing 

 chlorine over bromine, and condensing the vapours into a 

 liquid, and then allowing the vapour of this to act upon lime, 

 a solid may be obtained having all the properties of the Ame- 

 rican accelerator ; or by combining the chloro-iodide of lime 

 with a little of the bromide, a mixture similar to that of M. 

 Guerin's may be produced : but I greatly prefer, and would 

 recommend the pure bromide of lime, it being, as I believe, the 

 quickest accelerating substance at present known. By slightly 

 colouring the plate with the chloro-iodide, and then exposing 

 it for a proper time over the bromide, proofs may be obtained 

 in a fraction of a second, even late in the afternoon. A yel- 

 low colour should be given by the use of the first substance; 

 and the proper time over the bromide is readily obtained by 

 one or two trials. With about a drachm of the substance in a 

 shallow pan, I give the plate ten seconds the whole of the 

 first day of using the preparation, and add about three seconds 

 for every succeeding one. The compound should be evenly 



* I call this substance bromide of lime, although there is a difficulty 

 as to the composition of bleaching powder, and which would also apply to 

 the compounds I describe. Some chemists regard the chloride of lime to 

 be a compound of lime, water and chlorine. Balard thinks it is a mixture 

 of hypochlorite of lime and chloride of calcium; and the view of Millon 

 and Prof. Graham is, that it is a peroxide of lime, in which 1 equivalent 

 of oxygen is replaced by 1 of chlorine. 



