Page 25

MODERN DEVELOPERS

435

retain its characteristic qualities for days. When made up in developing solutions where the sodium carbonate predominates, pure paramidophenol-hydrochloride has excellent keeping quality. If the salt is impure, however, it will be necessary to have the sodium sulphite in excess, which, however, is detrimental to the developing power of the solution. As paramidophenol developers are Pe~:ilita~ties generally compared (as to their practical efficiency) with the familiar (Germanmade) metol developer, it is important to note here two peculiarities of paramidophenol which materially influence any comparison of the two developers in use. First: When paramidophenol is dis"Siowing up" ¡ SA? di um sup 1 h"1.te, or sul ph"1te "Speeding up" so1ve d m and potassiUm or sodium carbonate solutior>s, thete results a formation of tht true paramidophenol base in the solution. This robs the solution of its developing power in some degr<!e, so that such developers are said to "slow up" or "run down" more quickly than metol developers. It is not so in fact, as the apparently exhausted developing solution can be speeded up by the addition of small quantities of sodium hydrate (caustic soda). This redissolves the paramidophenol base first precioitated and makes it effective again for development. A saturated solution of sodium hydrate can be kept on hand and conveniently used for this purpo~e as needed, just as we use a 10 p~r cent solution of potassium bromid~ for reftraining development. With this addition of caustic soda as needed, it will be found that paramidophenol (hydrochloride or sulphate salt) approximates metol in developing power and efficiency. .. Second: It is often advised to use SeDSttive to paramidophenol "the same as metol " . Potass. Brom. â&#x20AC;˘ f II â&#x20AC;˘ t.e. rep1acmg the amount o meto1 ca ed for in any formula by an equal amount of paramidophenol salt. This is radically wrong. Where the makers give a definite formula, follow the formula as to the amount of paramidophenol required. Further, paramidophenol, unlike metol, is extremely sensitive to the restraining and retarding action of potassium bromide,

Modern Photographic Developers  

A Practical Handbook to the New Developers Telling What They Are and How to Use Them with Reliable Formulae by The Photo Miniature, January...

Modern Photographic Developers  

A Practical Handbook to the New Developers Telling What They Are and How to Use Them with Reliable Formulae by The Photo Miniature, January...

Advertisement