CENTRAL SCIENTIFIC CO., CHICAGO, U. S. A. 



401 



No. 10372. 



No. 10376. 



No. 10380. 



No. F937. 



No. 10396. 



1037-2. BOILING POINT APPARATUS, Jones, with ground in stopper and side tubulation $4.00 



10376. MOLECULAR WEIGHT DETERMINATION APPARATUS, McCoy, consisting of a graduated 

 inner vessel and jacket with rubber connection between. (See Journal of American Chemical 



Society, VoL XXII, for April 1900) 7.00 



10380. MOLECULAR WEIGHT DETERMINATION APPARATUS, Menzies, for determining molecular 

 weights by measurements of the vapor pressure. The apparatus consists of a graduated inner 

 vessel and outer jacket ground together. It can be used for two purposes: (1) the deter- 

 mination of the molecular weights of dissolved substances by measuring the lowering of vapor 

 pressure of the solution; (2) the determination of molecular weights of easily volatile sub- 

 stances by measuring their vapor pressures. It requires no thermometer or accessory appar- 

 atus, and can be supported on any ring stand. A complete determination requires only from 



30 to 40 minutes including the time of weighing. Complete as described 8.00 



F937. OSMOTIC PRESSURE TUBE, University of Chicago form, consisting of a glass tube of small 

 bore 5 feet long, with side arm with stop-cock and funnel tube. Complete with membrane for 



attachment to lower end 4.50 



F937A. ANIMAL MEMBRANES for use with No. F937 each .25 



POLARIZING APPARATUS, see Polariscopes. 

 PYCNOMETERS, see Bottles, Specific Gravity. 



RESISTANCES AND RHEOSTATS, see general heading Electrical Instruments. 



10396. SURFACE TENSION APPARATUS, simple form, with straight capillary tube of fine bore, glass 

 scale graduated in mm and immersion tube with side arm and rubber stopper. (See Findlay's 



Practical Physical Chemistry, page 91) 2.50 



THERMO-REGULATORS, see general headiug Thenno-Regulators. 

 10408. THERMOSTAT BATH, Aquarium Type, DeKhotinsky Electrically Heated and Regulated 



(Patented), with precision mercury thermo-regulator and sensitive iron clad relay. 

 Construction: The bath in constructed of heavy plate glass cemented in a frame work of angle 

 iron, with supporting legs of heavy cast iron bolted to the frame. The bottom is also of 

 plate glass set in Portland cement, supported by a plate of reinforced iron. The cement used 

 to hold the glass sides is a special composition which remains plastic, preventing any possi- 

 bility of leakage due to drying. Extensive experiments conducted at the University of Chi- 

 cago have shown the lack of necessity for heat insulating material around a bath for use at 

 temperatures from 10 to 60"C. For this reason, we have abandoned the old type of con- 

 struction and have adopted the aquarium style of bath, because of its superiority in render- 

 ing the interior of the bath visible from any position and admitting light to every corner. 

 The bath should be filled with distilled water to avoid the formation of deposits on the glass 

 sides. 



Stirring is accomplished by means of a high speed turbine stirrer of nickel-plated brass, which 

 takes water from the bottom of the bath at the rate of 45 liters per minute and delivers it at 

 the top with an expenditure of energy of 45 watts. An extra pulley is provided at the top 

 of the shaft to connect with stirrers in any apparatus placed in the bath. 



Heating of the bath is effected by means of four electric heating units inserted in seamless 

 brass tubes, fastened together in sets of two and attached by machine screws to the side. 

 These are connected in parallel, two of them being automatically switched on and off by the 

 relay. In order to maintain the temperature through warm weather or at temperatures below 

 that" of the room, two cooling coils are provided made of nickel-plated brass tubing of 6 mm 

 inside diameter and 20 meters in length, which lie close to the sides and bottom of the bath, 

 entirely out of the way. Through these coils may be passed city water or iced water to 

 maintain the desired temperature. 



Temperature control is secured by means of the DeKhotinsky precision thermo-regulator, con- 

 sisting of two solid drawn steel tubes, covered with brass, and connected to a common head. 

 To this is attached a glass capillary with regulating cap, by which the platinum point may 

 be raised and lowered to change the temperature setting. Coarse regulation may be effected 

 by turning the knurled screw by which the capillary is attached to the regulator head, thus 



