334 HOW TO SEE WITtf THE MICROSCOPE. 



in the operation for sugar this is not the case. There- 

 fore fill the burette to the " " mark with the graduated 

 solution of grape sugar. Into the measuring bottle 

 before described measure 66 grains ot the copper solu- 

 tion, the proper height being marked on the bottle with 

 a file. Add of the copper solution to that in the meas- 

 uring bottle to make the volume equal to 100 grains. 

 We then have 100 grains of the standard solution mixed 

 for use, and which are equivalent to J grain of sugar. 

 Pour the standard solution from the measuring bottle 

 into the largest test tube ; rinse the former with a little 

 water, and add this to that in the test tube, bringing 

 the latter over the spirit lamp ; heat to the boiling point, 

 and notice, first, if the standard solution retains its 

 clear blue color; if so, proceed to tritate, adding from 

 the burette a few drops at a time, bringing the mix- 

 ture, after each addition, to the boiling point. Con- 

 tinue thus, adding from the burette until the blue 

 color of the mixture in the test tube shall have almost 

 entirely disappeared. At this stage of the decom- 

 position of the copper the mixture in the tube will 

 have become thick and of a greenish yellow color, and 

 will show but little disposition to settle clear. Now 

 add cautiously a few drops from the burette ; bring to 

 the boiling point again, and, holding the tube in an in- 

 clined position near a sheet of white paper, observe the 

 thin edge of the liquid as to color. Should there appear 

 a trace of the blue yet, continue the addition from the 

 burette, and also the heat, until the last trace of the 

 blue shall have disappeared. Resting the tube in a ver- 



