A Manual Of Photography

PRACTICE OF PHOTOGRAPHY. 246 this, some have recommended the pan to be kept at a low temperature in a freezing mixture; and M. Daguerre, communication to the French Academy of Sciences, recon- mends the plate to he heated: hut in practice both these are found to he unsuccessful. (See Lerebours Traite lh“ It appeared to me, that if we could avoid the Eof water altogether in the accelerating mixture, not only would the.dif- ficulty I have mentioned be avoided, but a much more sensitive surface would be obtained on the plate. With this view I endeavoured to combine bromine with lime, so as to form compound analogous to bleaching powder In this I was successful, and find that bromine, chloride of iodine, and iodine may be united with lime, forming compounds having propertie similar to the so-called chloride of lime..bromine “The bromide of lime1 may be produced by allowing bromine vapour to act upon hydrate of lime for some hours : the most convenient method of doing this is to place some of he hydrate at the bottom of a flask, and then put some bromine into a glass capsule supported a little above the hmm 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« Fah.: the lime gradually assumes »beautiful scarlet colons and acquires an appearance very similar to that of iodide of mercury. The chloroiodide of lime may be formed in the same manner: it has a deep brown colour. Both these compounds, 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.,, .i„ “ Those daguerreotypists who use chlorine in combination with bromine, as in Woolcott’s American mixture or M. Guerin’s Hungarian solution, which is a compound of bromine, chlorine and iodine, may obtain similar substances in flic 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 hme, a solid may be obtained having all the properties of the Amènes 1 «I can this substance bromide of lime, although .there is a «y as to the composition of bleaching powder, and whieh wouid ào appto ÄGraham is, that it is a peroxide of lime, in which one exilât of oxygen is replaced by one of chlorine.