Journal of Applied Microscopy. 



93 



Hardware Co., Ann Arbor, Mich., at a 

 cost of about $3.00. It is designed to be 

 used in connection with a thermostat, 

 and with It the temperature may be held 

 constant within 0.1°C. With this appa- 

 ratus and Novy's thermo-regulator, it 

 Is possible to maintain constant tem- 

 peratures in an air bath at 50°C. and an 

 oven at 150° at the same time. The 

 dimensions can be varied to suit the 

 purpose of the operator, but those here 

 given will be found suited to the usual 

 needs. The outer vessel or pail is six 



fij. ^/v- rop or / IV A/5/? 



inches (or 15 cm.) in diameter, and seven 

 inches (18 cm.) deep. Through the cen- 

 ter of the bottom, three tubes enter, ris- 

 ing five and three- quarter inches (14.5 

 cm.) above the bottom. Beneath it, the 

 tubes bend at right angles and may 

 •diverge or run horizontally in any con- 

 venient direction. Two of these run a 

 short distance beyond the vessel, termi- 

 nating in stopcocks, and serve as exit 

 tubes for the gas. The third, which is 

 the inlet tube, bends upward at the 

 lower edge and extends three inches (8 

 cm.) above the top of the outer vessel, 

 turns outward at right angles again, 

 and terminates in a stopcock placed 

 horizontally. To this stopcock a four- 

 Inch (10 cm.) lever arm is attached. On 

 the inside three vertical U-shaped 

 grooves are soldered, extending three 

 inches (8 cm.) above the top. The tub- 

 ing should be not less than one-quarter 

 inch (7 mm.) internal diameter. 



The inner vessel or float is five inches 

 (13 cm.) in diameter, and six inches 

 (15 cm.) deep. On the outside three 

 vertical fianges are soldered, correspond- 

 ing to the three grooves in the outer 

 vessel, and projecting sufficiently to 

 prevent rotation or lateral motion of 

 the inner vessel, but allowing it to move 

 freely up and down. To the top of the 

 float is soldered a stiff wire ring, and 

 this is connected to the end of the lever 

 arm of the stopcock described above, by 

 means of a stiff wire of such length that 

 the valve is wide open when the float 

 is at its lowest position. The float with 

 attachments should weigh about twen- 

 ty-five ounces (700 grms.), under which 

 weight the gas will be delivered at about 



40 mm. pressure, but by means of con- 

 venient weights placed upon the float, 

 the pressure at which the gas is deliv- 

 ered may be varied at will. In the 

 laboratory here the maximum observed 

 pressure in the gaspipes was 87 mm., 

 and the minimum 40 mm., measured on 

 a water manometer. 



The outer vessel is to be fllled with 

 water to the depth of about 13 cm., 

 five inches (less than the height of the 

 tubes inside), or, if desired, glycerine 

 or liquid paraffin may be used, thus 

 avoiding evaporation. This apparatus 

 may be improvised in any laboratory by 

 using glass jars and tubes. Thus, two 

 battery jars with straight sides and 

 whose diameters differ by an inch serve 

 as pail and float. Instead of entering 

 through the bottom, glass tubing is bent 

 as herewith shown (see Fig. 4), and 



enters between the two vessels. Three 

 such tubes are bent and placed at equal 

 distances from each other. The tubing 

 should have an external diameter a lit- 

 tle less than half the difference between 

 the internal diameter of the large jar 

 and the external diameter of the small 

 one, and should extend 10 cm. (four 

 inches) above the top of the outer ves- 

 sel, serving instead of the flanges and 

 grooves. A glass stopcock with as large 

 a bore as possible, is clamped rigidly in 

 convenient position above the appara- 

 tus, and to it a lever arm of light wood 

 is attached, which rests on the float and 

 operates the valve. 



The operation of the apparatus is as 

 follows: 



One of the exit tubes may be con- 

 nected with a. manometer, or both may 

 go to burners as may be desired. Gas 

 enters through the stopcock and long 

 tube into the container or float, and in 

 so doing lifts the float, at the same time 

 closing the valve. If the outlets are 

 closed, the float will rise until the valve 

 is entirely closed, in which position it 

 will stand. When the exit tubes are 

 opened the float falls, reopening the 

 valve, admitting gas at the same rate 

 at which it is consumed, and delivering 



