Sil Horwitz (silh@iag.net)
Sat, 05 Jun 1999 22:00:29 -0400
At 99/06/05 08:17 PM -0400, Bob Schramm wrote:
>A quick way to detect chlorine and estimate its strength is to make up a
>10% solution of silver nitrate in distilled water. Keep it in an amber
dropping
>bottle. Put a little tap water in a small beaker or test tube and add a few
>drops of AgCl solution. If there is chlorine present it will percipitate
^^^^^^ (don't you mean AgNO3? AgCl is silver chloride, as you
know.)
>silver chloride (a white solid) i.e. the solution will turn "milky." The
>milkier it gets, the more chlorine. After doing this with various samples of
>tap water you will be able to judge when the Cl content is high.
Don't confuse "chlorine" (the gas) with "chloride" (the ion). Yes, silver
nitrate will react with chlorides to form the very insoluble silver chloride.
(This is a good test to check if chlorides, such as those from a water
softener, are present.) But chlorine gas may not necessarily react with the
silver ion, which could even act as a catalyst to form complex chlorine
compounds such as the very poisonous gas, phosgene. Silver ion + chloride ion
is a very simple reaction, but silver ion + gaseous chlorine is definitely not.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net
Visit http://www.psa-photo.org/
Personal page: http://www.iag.net/~silh/
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