Picric acid is stored under a layer of water to prevent an explosion.
What is the right way to measure the amount of picric acid that taken out? It is wet and containing water.
If accuracy is not essential, weigh a small amount drained for a fixed time but still wet, and then weigh again dried, to find the ratio of wet-to-dry weight (carefully disposing the dried, sensitized, explosive without destroying the scale or personnel).
Though this could give a rough idea of the actual dried weight, it would vary from batch to batch and with temperature.
Find some nice instruction:
As Picric Acid stored under layer of water, we could know it's concentration in the water. It should be enough for most of the applications.
Temperature ° C. grams picric acid/100 grams solution