This is a test for chlorides in NaOH sample.

Question

1.0g of NaOH was dissolved in 5ml of distilled water, acidified with 4ml of dilute nitric acid and diluted to 15ml with distilled water. This mixture was poured into a test tube containing 1ml of AgNO3 solution.
However, I obtained a dirty brown ppt. Do you have any idea what the problem might be?
Thanks.

Answer 1

Yes. You did this in light, the silver chloride is photosenstive, it darkens when exposed to light. Brown is not unusual (dark bluish, with slight yellow).

Answer 2

I obtained a lot of dirty brown ppt the moment the mixture was poured into AgNO3 solution. Does this mean my NaOH sample contains a lot of chlorides? Could other silver halides be present?

However for my control solution of 50ppm sodium chloride solution,a turbid solution (cloudy white ppt) was obtained after standing for a while.

Please advise how should I conduct the test?

Answer 3

With my observation it turns to be dirty brown
.