unknown solution造句怎么写

a measured amount of a solution of unknown concentration is added to a known volume of a second solution until the reaction between them is just complete; the concentration of the unknown solution (the titer) can them be calculated.

The solution of known concentration is gradually added to the unknown solution from a burette (a long measuring tube with a valve at the bottom) until the equivalence point (end point) is reached. The amount of the unknown substance can then be calculated.