TESTING OF THE DIALY5IXG TUBE- 159 



hvdnn must be dissolved with distilled and sterilized 

 water; this solution is poured into the measure, and 

 the tube is again rinsed several times, after which 



_ 



the measure is filled up nearly to the mark. Xin- 

 hydrin dissolve - - aringly in water, and in order I 

 dissolve it quickly it must be heated a little. F r 

 this purpose it is best to stand the measure in the 

 incubator. As soon as the solution is effected, the 

 contents are . and filled up to the mark on th^ 



flask. 



The ninhvdrin solution is not absolutely stable. 

 I: is liable to infection, and is a".- nsitive to the 

 action of liglv . I: mav be kept in a brown flask, 

 but thi- is not ne- ess - > long as one prepar - 

 <~>nlv 10 c.c. at a time, a quantitv which is quickly- 

 used up. 



After all the test-1 es containing 10 c.c. of the 

 dialvsate have been filled with o'2 c.c. of the ninhv- 

 drin solution, a boiling-stick is placed in each. The 

 latter is absolutelv essential, because onlv a verv 

 even ebullition will produce a properly comparable 

 colour reaction. The boiling-sticks used in the trade 

 are divided into segmen'- about 10 cm. long; these 

 must be boiled in distilled water, dried at 6> 

 ~ - ' *.. and kept in a tightlv closed glass vessel. Boil- 

 ing-sticks must not be stored in a damp condition : 

 for on the one hand their use in this state mav give 



o 



rise ' error, owing 1 to the uneven amount - :' 



