Sentence:  &#91;[https://books.google.com/books?id=9rpMo4As8z8C&pg=PA51 page 51]&#93; The following are the results of experiments made with rhubarb, to ascertain the best modes of detecting it in the urine and blood, and the time it takes to pass from the stomach to the urinary bladder. [...] &#91;[https://books.google.com/books?id=9rpMo4As8z8C&pg=PA52 page 52]&#93; In 17 minutes, half an ounce of urine was voided, which when tested had a light <WSD>tinge</WSD>. In 30 minutes another half ounce was made, in which the <WSD>tinge</WSD> was stronger; and in 41 minutes a third half ounce was made, in which it was very deep. In an hour and ten minutes 7 ounces were voided, in which the <WSD>tinge</WSD> of rhubarb was very weak, and in two hours twelve ounces were voided, in which it was hardly perceptible. 
Meaning of the word marked with <WSD> tags:  The degree of vividness of a colour; hue, shade, tint.