83 MOUNTING AND LABELING. 



When the volatile products have evaporated, the balsam is broken into small 

 pieces or powdered in a mortar and mixed with about an equal volume of xylol, 

 turpentine or chloroform. It will dissolve in this and then should be filtered 

 through absorbent cotton or a filter paper, using a paper funnel.* The balsam is 

 too thin in this condition for mounting, but so made for the sake of filtering it. 

 After it is filtered it is evaporated slowly in an open dish or a wide-mouth bottle 

 or jar till it is of a syrupy consistency at the ordinary temperature. It is then 

 poured into a bottle with a glass cap like a spirit lamp. For use it is put into a 

 small spirit lamp (Pi. V, Fig 47). 



The xylol is much the best substance to use for thinning the balsam. Such 

 xylol balsam, as it is then called, may be used for mounting any object suitable 

 for balsam mounting. The dehydration must be very perfect, however, as xylol 

 is wholly immiscible with water. 



\ 192. Clearing Mixture (g 175). — One of the most satisfactory and generally ap- 

 plicable clearers is made by mixing carbolic acid crystals (Acidum carbolicum , 

 A. phenicum crystallization) 40 cc. with rectified oil of turpentine {Oleum tere- 

 binthinae rectification) 60 cc. 



\ 193. Shellac Cement. — Shellac cement for sealing preparations and for making 

 shallow cells {\\ 167, 168) is prepared by adding scale or bleached shellac to 95 

 per cent, alcohol. The bottle should be filled about half full of the solid shellac 

 then enough 95 per cent, alcohol added to fill the bottle nearly full. The bottle 

 is shaken occasionally and then allowed to stand until a clear stratum of liquid 

 appears on the top. This clear, supernatant solution is then filtered through 

 absorbent cotton, using a paper funnel (jj 189), into an open dish or a wide-mouth 

 bottle. To every 50 cc of this filtered shellac 5 cc. of castor oil and 5 cc. of Vene- 

 tian turpentine are added to render the shellac less brittle. This filtered shellac 

 will be too thin and must be allowed to evaporate till it is of the consistency of 

 thin syrup. It is then put into a capped bottle and for use into a small spirit 

 lamp (PI. V, Fig. 47). In case the cement gets too thick add a small amount of 95 

 per cent, alcohol or some thin shellac. 



\ 194. Liquid Gelatin. — Gelatin or clear glue 75 to 100 grams. Commercial 

 acetic acid (No. 8) 100 cc, Water 100 cc, 95 per cent, alcohol 100 cc. Glycerin 15 

 to 30 cc. Crush the glue and put it into a bottle with the acid, and set in a warm 

 place, and shake occasionally. After three or more days add the other ingredi- 

 ents. This solution is excellent for fastening paper to glass, wood or paper. The 

 brush must be mounted in a quill or wooden handle. For labels, it is best to use 

 linen paper of moderate thickness. This should be coated with the liquid gelatin 

 and allowed to dry. The labels may be cut of any desired size and attached by 

 simply moistening them as in using postage stamps. 



Very excellent blank labels are now furnished by dealers in microscopical sup- 

 plies, so that it is unnecessary to prepare them one's self except for special pur- 

 poses. 



* For filtering balsam and all resinous and gummy materials, the writer has 

 found a paper funnel the most satisfactory. It can be used once and then thrown 

 away. Such a funnel may be very easily made by rolling a sheet of thick writing 

 paper in the form of a cone and cementing the paper where it overlaps, or winding 

 a string several times around the lower part. Such a funnel is best used in one of 

 the rings for holding funnels. 



