The Nylander test is a medical test for glucose in the urine, making use of a solution that contains bismuth subnitrate. The solution forms a black precipitate in a positive reaction.
To prepare the reagent for the test, dissolve four grams of sodium tartrate in 100 cubic centimeters of a ten percent caustic soda solution. Then add two grams of bismuth subnitrate. Heat the mixture to 50 degrees Celsius and filter after cooling. Preserving the reagent, even for months, leaves it unaltered.
The test works on the principle that when a subnitrate of bismuth comes in contact with grape sugar in a boiling alkaline solution, it reduces to black metallic bismuth. For the test, boil 10 cubic centimeters of urine with 1 cubic centimeter of the reagent for two minutes.
The conclusion of the test is that when sugar is present, there is a brown to black colouration of the fluid where the metallic bismuth settles down. If the dark coloration occurs as the fluid is cooling down, it does not prove the presence of sugar. The reaction takes place when the proportion of sugar in the urine is 0.1 percent. If the Nylander test gives a negative result, there is no need to do any further test.