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Silver Subhaloids

prepared, treating and guntz

SILVER SUBHALOIDS Chemists have usually considered that the action of light upon the silver haloids was the splitting off of a molecule of the halogen and the formation of a salt with consequent lower pro portion of halogen, which may be represented by the formula, 2Agel = Cl or 4Age1 They named the new compounds subhaloids. For many years the existence of such subsalts was denied, because the actual existence of silver suboxide could not be definitely proved. In 1891 Guntz was able to prepare the sub fluoride or by heating silver fluoride AgP in a sealed tube at a temperature not above P. with finely divided silver and also by electrolysis of a saturated solution of silver fluoride, using silver electrodes. By treatment of this salt, a yellow crystalline powder, with steam he was able to prepare the suboxide Ag,O, and Weltzien prepared a silver hydroxide by treating it with hydrogen peroxide. Prom the subfluoride Guntz also prepared the subchloride by passing dry hydrochloric acid gas over it, or by treating it with the volatile chlor ides of carbon, silicon, and phosphorus, etc. The

subchloride varies in colour from deep violet red to violet black, and when heated it splits up into ordinary silver chloride and metallic silver potassium cyanide; and sodium hyposulphite produces a similar reaction with the solution of the chloride. Silver subiodide was also prepared by Guntz by the action of hydrogen iodide. The actual formation of these subhaloids is a strong argument in favour of the subhaloid theory of the latent image (which see). The subbromide may be prepared in the same way as the sub chloride, or by treating the subfluoride with phosphorus tribromide (Heger). Liippo-Cramer claims to have prepared a subbromide, by treating mercurous bromide with silver nitrate.