MICRO-BURNERS 



155 



convenient. The usual form employed in blowpipe analysis 

 provided with a platinum tip should be chosen and if in addition 

 it can be fitted with a hot-blast attachment its usefulness will 

 thereby be greatly increased. 



Where the work table is supplied with compressed air a minia- 

 ture blast lamp of the type shown in Fig. 88 is an invaluable aid 

 in fusions, production of high temperatures, preparation of tiny 

 blown glass apparatus, etc. ; having two joints it can be quickly 

 adjusted to almost any position and can even be employed to 

 heat material directly under the microscope, although such oper- 

 ations are best performed by means of an electric current since 

 the heat may thus be far better localized. 



Heating preparations while subjecting them to observation 

 through the microscope may be accomplished by means of the 

 electrically heated hot stage (see page 222) or by a tiny flame 

 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 

 moderately high powers and tem- 

 peratures 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 typ- 

 ical instrument of this sort is shown 

 in Fig. 29, page 71. 



Small Tongs. — As a substitute 

 for crucible tongs for holding plati- 

 num foil, cups, etc., a pair of com- 

 pression arterial forceps, Fig. 89, will be found to be a valuable 

 addition to the equipment. Forceps of this sort hold thin 



Fig. 89. Surgical Compression 

 Forceps. Convenient for Hold- 

 ing Small Platinum Cups or 

 Pieces of Foil. 



