660 SEC. 13. CHEMISTRY. 



in this instrument (and described in the Zeitschrift for 1870, p. 609) are as 

 follows : 



(1.) In the place of the two quartz-wedges sliding against one another in the 

 earlier instruments, and which cany the scale and vernier, these instruments 

 have the wedges so arranged that only one of them carrying the scale is 

 movable, the other bearing the vernier is fixed. By this means a much firaier 

 motion of the first wedge is secured, and the so-called dead-motion of the 

 setting-screw does not easily occur. In consequence of this the zero point of 

 both wedges remains unaltered, which is a matter of considerable importanc3. 



(2.) The above-mentioned vernier resting on a firmly fixed quartz-wedge 

 is movable within definite dimensions, by means of a key, without the position 

 of the wedge itself being changed. In this way an accurate adjustment to the 

 zero point is easily accomplished. 



(3.) For the more convenient reading off of the experimental numbers 

 obtained, a small round magnifying mirror is fixed above the scale. 



(4.) To prevent any side rays interfering with the readings, all light is kept 

 out by a completely light-tight sliding casing fitted over the observation tubes. 



2668. Mitscherlich's simple Polarising Apparatus for 



use in sugar refineries. Dr. C. Scheibler, Berlin. 



2669. Scheibler's Apparatus for the estimation of Car- 

 bonate of Ziime in bone charcoal, as well as for the quantitative 

 volumetric analysis of carbonates generally. 



Dr. C. Scheibler, Berlin. 



This apparatus was described by Scheibler in the above-mentioned Zeit- 

 schrift for 1859, p. 285, and for 1861, p. 525. 



2670. Scheibler's Apparatus for the volumetric esti- 

 mation of Carbonic Acid contained in the gases of saturated 

 solutions. Dr. C. Scheibler , Berlin. 



Described in Zeitschrift for 1866, p. 644. 



2671. Scheibler's Apparatus for estimating the Refinery 

 Value of raw Sugar. Dr. C. Scheibler, Berlin. 



Described in Zeitschrift for 1872, p. 297, and 1873, p. 304. 



2672. Stammer's Colorimeter for estimating the Colour 

 of Liquids. Dr. C. Scheibler, Berlin. 



2673. Hydrostatic Balance for estimating the Density of 

 Sugar solutions and other liquids. Dr. C. Scheibler, Berlin. 



Described in Zeitschrift for 1870, p. 264. 



2674. Brix's Standard Saccharometer, consisting of three 

 hydrometer tubes and a thermometer packed in a case. 



Dr. C. Scheibler, Berlin. 



2675. Gerlach's Standard Saccharometer. 



Dr. C. Scheibler, Berlin. 



