174 SEC. 5. MOLECULAR 'PHYSICS. 



water, as the latter flows freely away after use. The instrument may be con- 

 nected by a simple screw arrangement with the boiler. 



673e. Four-fold Control Manometer. 



C. D. Gabler, Hamburg. 



This manometer, consisting of two manometers of the above construction, 

 combined one with the other, offers the greatest possible safety in controlling ; 

 because, if only two-fold action be required, the one pair of manometers 

 can be shut off by closing the stopcock, and may thus be used as reserve or 

 control of the manometer thence used. The connexion with the boiler 

 flange is performed by means of the accompanying two thumb nut-screws. 



673f. Control Manometer, showing the inner construction. 



C. D. Gdbler, Hamburg. 



Shows the extremely simple construction of the inner mechanism of the 

 manometers described above. 



674. Alcoholometer, consisting of two cylinders of ebonite 

 and brass, keyed together. G. Recknagel, Kaiser si autern. 



This instrument is not liable to break, and answers all requirements of 

 accuracy in reading. 



675. Areometer of ebonite and brass, with adjustable cylinder. 



G. JRecknagel, Kaiser slautern. 



This not being liable to be broken can be used for educational purposes as 

 well as for practical application. 



The level upper terminal plate is adapted for the addition of small weights 

 by means of which the value of the divisions can be demonstrated. The 

 instrument, moreover, is arranged with a cylindrical slide, Avhich can be 

 extended to the double volume of the divided spindle. If the scale is over- 

 run, the slide is to be pulled out a volume more, and the scale is then again 

 at disposal for use. 



Eor instruction and practice the most suitable is the uniform scale of the 

 Gay Lussac areometer. As, however, there is space for four scales, the 

 others can be arranged for direct indication of specific weights, or, like the 

 present models, for alcoholometry. 



676. Areometer Case, containing three standard areometer- 

 cylinders, for determining the specific gravity of all kinds of 

 liquids, with indicator scale fused into them. W. Zorn, Berlin. 



677. Areometer. The indicator scale is not fused into the 

 glass, but fastened only with sealing-wax. W. Zorn, Berlin. 



Each of these areometer-cases contains three glass spindles, which, loaded 

 at the top in a similar manner to Nicholson's metal spindles, with weights, 

 indicate with the greatest accuracy the specific weight of all liquids. 



The liquid to be tested must be brought to a temperature of 15 Celsius ; if 

 one of the spindles is inserted in the liquid, so many weights must be placed 

 on the glass plate as are required to make the spindle sink as far as the black 

 mark on the milk-white glass line iu the neck of the spindle. 



The lightest spindle embraces all liquids from 0'650 to 1,000; if this 

 has been used, 0-650 must be added to the weight placed on the spindle. If 

 the medium (1,000) spindle has been employed, 1,000 must be added to the 

 weight, and at the heaviest (1,400) spindle, 1,400 must be added to the weight 

 placed on the same. The sum obtained will give the specific weight of the 

 liquids with an accuracy extending a little over the third decimal. 



