Verification of aldehydes with Tollens' test

Chemicals needed

Ammonia solution 10% GSATZEND.gif (935 Byte)GSUMWELT.gif (758 Byte)  N    R 24-50     S (1/2)-26-36/37/29-45-61

benzaldehydeGSGESUND.gif (476 Byte) Xn    R 22    S (2)-24

sodium hydroxide solution 7,5%  GSATZEND.gif (935 Byte) C    R 35     S (1/2)-26-37/39-45

silver nitrate solution, verdŁnnt  GSGESUND.gif (476 Byte) Xi GSUMWELT.gif (758 Byte)  N    R 34-50/53     S(1/2)-26-45-60-61

One can also verify other aldehydes, in this case heating may be necessary.

Equipment needed

test tube

Test procedure



Due to the addition of ammonia, silver(I) which would otherwise be precipitated as hydroxide, is complexed. The proof is based on the reducing character of aldehydes and is therefore not restricted to these. The aldehyde is oxidized to carboxylic acid, while silver(I) is reduced to silver(0).


Elementary silver precipitates


Reference will be added