1881.] Spectrum on the Haloid Salts of Silver, Sfc. 175 



silver bromide. Fig. 27 represents the action of the spectrum on 

 silver bromide paper, prepared as above, which has been washed. 

 Whether development took place by acid developer or by ferrous 

 citro- oxalate, no difference was observable. Fig. 28 shows the same 

 with a short exposure. When the paper was washed and treated with 

 potassium bromide and then exposed, we have as a result figs. 31 

 and 32. The slight difference in the pairs of figures results from the 

 presence in one case of inorganic matter combined with silver, and in 

 the other case its absence. 



When a plate is coated with collodion containing cadmium bromide, 

 zinc bromide, or potassium bromide, and placed in a strong silver nitrate 

 bath, and developed with either acid developer or with ferrous citro- 

 oxalate, we get curves similar to figs. 31 and 32. The same figures 

 also represent the action of the spectrum on collodio-bromide emul- 

 sions transmitting orange light by any kind of development. This 

 applies equally whether the plate be exposed wet or dry, or whether- 

 exposed in the presence of silver nitrate or other inorganic sensitisers. 



Figs. 29 and 30 show the results obtained when using gelatine 

 bromide plates with the silver bromide in the grey molecular state, 

 whether exposed with an inorganic sensitiser, or without, and 

 whether developed with an acid, alkaline, or organic iron developer. 



Figs. 33 and 34 represent the action on the blue-green molecular 

 form of silver bromide in collodion, when developed and exposed 

 under similar circumstances to the preceding case. 



It will be remarked that the direct visible action of the spectrum 

 and the developed image coincide. 



The effect of impurity in the bromide is not so marked as it is in the 

 iodide. The presence of iodide except in minute quantities is rare ; 

 the haloid most frequently present as an impurity being the chloride. 

 When the spectrum on the chloride is considered, it will be seen that 

 such an impurity is hardly possible to be detected, as the spectra 

 impressed on it are somewhat similar in general character to those 

 on the bromide. 



Silver Chloride. 



Paper was impregnated with a 10 per cent, solution of sodium 

 chloride and sensitised on a 10 per cent, solution of silver nitrate.. 

 Paper thus prepared was exposed to the spectrum in a damp state, 

 and also in a dry state, and the visible impression recorded. Fig. 35 

 shows the action. When the paper was exposed for twenty seconds to 

 diffused light a different curve as shown in fig. 36 was found ; an 

 approach to the same curve being also shown with very prolonged 

 exposure without the preliminary action of light. This is probably 

 due to the action of the diffused light in the prism.* 



* I have not taken into consideration the spectrum impressed on silver chloride 



