Silver salts, colors

Only three simple silver salts, ie, the fluoride, nitrate, and perchlorate, are soluble to the extent of at least one mole per Hter. Silver acetate, chlorate, nitrite, and sulfate are considered to be moderately soluble. AH other silver salts are, at most, spatingly soluble the sulfide is one of the most iasoluble salts known. SHver(I) also forms stable complexes with excess ammonia, cyanide, thiosulfate, and the haUdes. Complex formation often results ia the solubilization of otherwise iasoluble salts. Silver bromide and iodide are colored, although the respective ions are colorless. This is considered to be evidence of the partially covalent nature of these salts. 

Metastable cyanomethylnitrolic acid and its red color in basic water solution have already been observed by Steinkopf. Moreover, he postulated the existence of the silver salt AgNNtCM. The intermediate formation of the silver salt has also been postulated by Pillai and Boyer in the reaction of ICH2CN with AgN02 which finally gave NC—CH2—O—N=C(N02)CN, the only product which could be isolated . 

Iodine is used in many dyes and as a colorant for foods and cosmetics. Its silver salt is used in photographic negative emulsions. Other industrial applications include dehydrogenation of butane and butylenes to 1,3-butadiene as a catalyst in many organic reactions in treatment of naphtha to yield high octane motor fuel and in preparation of many metals in high purity grade, such as titanium, zirconium and hafnium. 

Acetone, Nitration. Krauz Stepanek(Ref 1) attempted to prepare terrani from ethane by nitration of acetone, but failed, instead, they obtained (after treating the resulting product with a silver salt) a very expl solid claimed to be Ag salt of acetylmethylnitrolic acid, also called a-nitro - a -isonitroso-acetone. Hass Hudgin(Ref 3) nitrated acet, using a vapor-phase nitration technique described in Ref 2. The high-boiling fractn from the nitration gave an odor of acetic acid, an acidic reaction in aq soln, a red color with ferric chloride and a yel salt with Ag nitrate soln,... 

The copper (I) and silver salts of tetrarodomercuric (II) add, H2[HgI, exhibit color changes with variations in temperature which are reversible in nature. 

Printing-out emulsions. These emulsions produce images on exposure without development. They are used largely for making portrait proofs which are distinguished by their red or purplish color. Emulsions of this type differ from others in that they usually contain silver nitrate, some free silver, silver salt of an organic acid and a weak free acid. These are known as P.O.P. Proof Papers. 

Another class of indicators, known as adsorption indicators, adsorb to (or desorb from) the precipitate or colloidal particles of the silver salt of the analyte at the equivalence point. The indicator anions are attracted into the counterion layer surrounding each colloidal particle of silver salt. Thus, there is a transfer of color from the solution to the solid or from the solid to the solution at the end point. The concentration of the indicator, which is an organic compound, is not large enough to cause its precipitation as a silver salt. Thus, the color change is an adsorption and not a precipitation process. Fluorescein is a typical example of an adsorption indicator in argentometric titration. 

Most salts of silver are relatively insoluble in water, the important exceptions being the low-melting nitrate and perchlorate, AgN03 and AgCiCL, and silver fluoride, AgF. These, as well as many other silver salts, are colorless but certain of the silver salts with relatively polarizable anions (Chap. 3), besides being insoluble in water, are brightly colored. Thus the colorless sulfate, chloride, and fluohorate of silver may be compared to the yellow iodide, the red arsenate and chromate, and the black sulfide. 

Color photography, now fully perfected, requires a developer like N,N -diethylphenylenediamine which reacts with silver salts. The oxidized derivative obtained reacts with a coupling agent made up of groups (-CH=) or (-CH2-) to produce the desired color. 

This base (as the trihydrochloride) reacted with hexachloroplatinic(IV) acid to form the salt, XXXIV, in which the central nitrogen atom becomes asymmetric attempts to resolve it not unexpectedly failed as this group would almost certainly have very low, optical stability. The salt, XXXIV, when treated with silver salts, lost hydrogen chloride with the formation of the salt, XXXV. With potassium tetrachloroplatinate(II), the salt, XXXVI (X = Cl), was obtained and was more readily isolated after treatment in solution with sodium bromide or iodide as the cream-colored XXXVI (X = Br) or XXXVI (X = I), respectively. The free base reacted with aquopentamminocobaltic trichloride to give the... 

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