USEFUL MICROSCOPE ACCESSORIES 



129 



obtained from a glass or quartz tube drawn out and bent up and 

 supported by the substage ring of the instrument, the rotating 

 stage having been removed to avoid injury and the preparation 

 supported on an asbestos plate provided with a small central 

 orifice for the passage of light. It is obvious that when moder- 

 ately high powers and temperatures are to be employed, the 

 objectives must be kept cool either by means of a strong blast of 

 cold air or by water jackets. To meet these conditions specially 

 constructed microscopes are obtainable; a typical instrument 

 of this sort is shown in Fig 7, page 29. 



Small Tongs. As a substitute for crucible tongs for holding 

 platinum foil, cups, etc., a pair of compression arterial forceps, 

 Fig. 75, will be found to be a valuable 

 addition to the equipment. Forceps 

 of this sort hold thin material tena- 

 ciously since they lock firmly in place, 

 and thus the fingers do not become 

 cramped during prolonged heat treat- 

 ments. 



Work Tables. The type of work 

 table chosen by the chemist upon 

 which to place his instruments and 

 apparatus for microchemical inves- 

 tigations will depend largely upon 

 his individual preferences or upon 

 the character of the work he is called 

 upon to perform. 



In general a table provided with FlGt ~ 5 . Surgical compression 

 an indentation or cut-out portion Forceps. Convenient for Hold- 

 along one edge will be found to pos- in s Sma11 Platinum Cups or 



. r . Pieces of Foil. 



sess many advantages over a simple 



straight edged table. The worker, sitting well up into the 

 cut-out, secures support for his arms and is enabled to sit up 

 straighter; thus he is subject to far less fatigue during long 

 observations and manipulations. Moreover, in the greater part 

 of microchemical analyses or examinations more or less corrosive 

 vapors or gases are apt to be given off which it is desirable to keep 



