Concentration of Picral
Concentration of Picral
(OP)
If I am adding 4 grams of picric acid to 100ml of ethanol, and the specific gravity of picric acid is 1.77, wouldn't the concentration of the resulting be 2.26%?
All the handbooks and manuals I have found call this a 4% picral solution.
What am I missing?
All the handbooks and manuals I have found call this a 4% picral solution.
What am I missing?





RE: Concentration of Picral
You might want to add 1 ml conc HCl if the picral doesn't give a good etch.
Don't make any more of the Picral than necessary and dispose of the remainder if it's not going to be used in short time. Picric acid can be explosive under certain conditions.
RE: Concentration of Picral
RE: Concentration of Picral
RE: Concentration of Picral
Since metallurgists like to keep things simple, 4 grams of picric powder (with moisture to prevent it from going ka-boom) is added to 100 ml of ethanol (with a density rounded off to 1) to make a 4% solution of picral. Whether it is really 5 wt%, 4 w/v % or just 2.26 volume % is immaterial in this process - it still works to etch the carbides present in my steel and it is quiet.