T W- 
 
[Reprinted from the Journal ofthe American Chemical Society, 
 Vol. XXI, No. i. January, 1899.] 
 
 [Contributions from the Chemical Laboratory of the University 
 
 of Illinois.] 
 
 iriPROVED APPARATUS, 
 
 By J. L. Sammis. 
 
 Received October 10, 1898. 
 
 BURETTE. 
 
 HE frequent use of Mohr’s burette with Geissler’s glass 
 
 1 stop-cock during the past summer called the writer’s 
 attention to two points which, it was thought, might be 
 improved. 
 
 The handle of the glass stop-cock, as usually made, is turned 
 toward the right. Right-handed persons usually find it easier 
 to operate the stop-cock with the left hand and stir or shake the 
 titrated liquid with the right. In order to facilitate this, the 
 stop-cock of a burette was cut off and sealed on again with its 
 handle toward the left. See Fig. i. 
 
 In titrating, much care has to be exercised lest the mark 
 upon the float should sink below the graduations on the 
 
IMPROVED APPARATUS. 
 
 43 
 
 scale of the burette. To render this impossible and to en- 
 able one to see more easily 
 the scale and the titrated 
 liquid at the same time, the 
 tip of the burette was elonga- 
 ted to about fourteen inches 
 by sealing in a piece of glass 
 tubing between the stop-cock 
 and the constricted extrem- 
 ity. This elongated tip was 
 bent to the front and a little 
 to the right just below the 
 stop-cock, and then upwards. 
 
 Two more bends were so 
 placed that the end of the tip 
 was about three inches in 
 front and one inch to the right 
 of the lowest mark upon 
 the fifty cc. burette. By 
 this arrangement, with the 
 stop-cock wide open, not a 
 drop of liquid will flow out after 
 the liquid meniscus in the 
 burette has reached the level 
 of the end of the tip, which, 
 as described, is just opposite 
 the fifty cc. mark of the 
 scale. If the tip be placed a 
 little higher up, say opposite 
 the forty-nine cc. mark, the 
 instrument may be used with 
 a float or without. The long 
 narrow burette with the new 
 tip can be held much closer to the table by the burette clamp, 
 and the easy reading of the upper end of the scale is thereby 
 facilitated. 
 
 electric heater adapted for use in ether extraction. 
 
 During the past year, a large number of extractions with 
 Sohxlet’s apparatus have been performed in this laboratory. In 
 
44 
 
 IMPROVED APPARATUS. 
 
 order to continue this operation during the night time without 
 the danger of fire, an electric heater was devised which could be 
 put in operation by closing a switch and which kept the water at 
 the proper temperature as long as desired. The heater (Fig. 2) is 
 made of coils of No. 24, soft iron wire, wrapped upon a brass 
 rod, and insulated from the rod and from each other by thin 
 sheet asbestos. The winding was done rapidly by placing in 
 
 the lathe chuck a brass rod six inches long and three-eighths of 
 an inch in diameter, laying a sheet of asbestos paper over it, 
 and winding on the wire, keeping the turns about one-thirty- 
 second of an inch apart to prevent short circuiting. Having 
 wound one coil, a second sheet of asbestos is put on, and a 
 second coil wound on it, and so on until the desired resistance is 
 obtained. The ends of the iron wire are soldered to short pieces of 
 No. 12 insulated copper wire which serve to bring in the elec- 
 tric current. The cylinder thus made is slipped into a closely 
 fitting tube of sheet copper and the ends of the latter are soldered 
 on. A small hole or notch is left at one end of the copper tube 
 through which the insulated wires pass. These copper wires 
 are pushed through a narrow piece of brass tubing about four 
 inches long, and the tubing is soldered to the copper cylinder in 
 a position perpendicular to the axis of the latter. The heater is 
 placed in a four-holed water-bath and the brass tube with the 
 copper wires is pushed up through a small hole made in one 
 corner of the top of the bath. The tube may be soldered to the 
 
J. L,. SAMMIS. 
 
 45 
 
 edges of the hole. The ends of the copper wires are made fast 
 to binding posts, screwed into a narrow strip of wood upon the 
 front of the battery of water-baths. 
 
 One heater is required for each four-holed water-bath, and the 
 heaters are connected in parallel. The length of the iron wire 
 in one heater is seventy feet, and its resistance when hot is 
 twenty-six ohms. The potential difference across the ends of 
 the heating coils is fifty-two volts, thus using two amperes of 
 current and 104 watts per heater. The heat generated is suffi- 
 cient to keep the water in the bath at 65° C., and the ether in 
 the extraction apparatus falls from the condenser at the rate of 
 twenty or twenty-five drops per minute. The currents from a 
 storage battery and from a 125- volt dynamo have been used to 
 run this apparatus with perfect success, and with little attention 
 and no risk of fire. 
 
 September 25, 1898.