﻿350 The Philippine Journal of Science mm 



The microburner is placed to the right of the microscope, 

 as usual, and to the right of the microburner and near the edge 

 of the table is placed a large crystallizing dish about 5 centi- 

 meters in height, full to the brim with water containing ice. 

 To the left of the microscope is placed a special apparatus for 

 regulating the temperature of the loop. 



This apparatus (fig. 18) consists of the brass tube T, to the 

 lower part of which is attached the brass cup C. This cup is 

 elliptical in horizontal section with a long diameter of about 

 8 centimeters and a short one of about 4.5 centimeters. The 

 tube T is held in the sleeve S, which is attached to the arm of 

 a simple microscope provided with a ratchet and pinion R. 

 By means of the ratchet and pinion, the sleeve and tube may 

 be raised and lowered through about 5 centimeters. The tube 

 may be raised or lowered in the sleeve; a joint at J allows the 

 cup to be swung aside. A Petri dish is placed beneath the 

 cup to receive waste water. The cup must be filled with water 

 containing snow or small pieces of ice. 



The pipette is now to be filled with mercury to the tip of 

 the capillary. Heat the loop gently in a flame, and immerse 

 the point of the capillary in mercury the moment all air is 

 expelled. With the tip still in the mercury, immerse about two- 

 thirds of the loop into the crystallizing dish containing ice 

 water and hold it in this position for a quarter of a minute or 

 so. Now remove the tip from the mercury, and immerse the 

 loop still farther into the ice water. The mercury in the capil- 

 lary will retreat 4 or 5 centimeters from the end. Make the 

 pipette point immediately, following as nearly as possible the 

 same technique as in the case of isolating pipettes. The loop 

 should remain in the ice water, and the arm next to the loop 

 may rest on the edge of the crystallizing dish. The arm should 

 be kept nearly horizontal and held with the right hand at a 

 point near the beginning of the capillary. The forceps, held in 

 the left hand, grasp the capillary. The microburner must be 

 slipped to a convenient distance from the dish. One may draw 

 the pipette more conveniently if seated low enough to bring the 

 eye near the level of the flame. 



For this work it is necessary to have a closed tip, coming 

 rather abruptly to a very fine point, a (fig. 19), A point more 

 tapering can be used as b (fig. 19), but such points are more 

 liable to become clogged with mercury, and do not allow of the 

 control of the dosage as well as the kind illustrated. One will 

 save time eventually by making a point of the proper form. 

 After a suitable tip is drawn, it should be turned at right angles 



