ETYM Old Fren. asai, essai, trial, French essa. Related to Essay.
An appraisal of the state of affairs; SYN. check, test.
In chemistry, the determination of the quantity of a given substance present in a sample. Usually it refers to determining the purity of precious metals.
The assay may be carried out by “wet” methods, when the sample is wholly or partially dissolved in some reagent (often an acid), or by “dry” or “fire” methods, in which the compounds present in the sample are combined with other substances.

ETYM Archaic. In this sense essay is now commonly used.
To analyze (chemical substances).
Analyze or evaluate (ore, etc.); judge the worth of; attempt.