EXAMINATION AND PRESERVATION MEDIA. 247 



448. Thickened Oil of Turpentine has been used as a mount- 

 ing medium by some workers. To prepare it, pour some oil 

 into a plate, cover it lightly so as to protect it from dust 

 without excluding the air, and leave it until it has attained a 

 syrupy consistency. 



449. GILSON'S Sandarac Media (La Cellule, xxiii, 1906, p. 

 427 : the formulae have not been published, on account of 

 the extreme difficulty of preparation, but the products are 

 on sale by Griibler & Hollborn, even if not listed). There 

 are three of these. They are air of them solutions of gum 

 Sandarac in " Camsal " and other solvents (" Camsal " is a 

 liquid formed by the mutual solution of the two solids salol 

 and camphor). 



(1) Camsal balsam (baume au camsal), propylic alcohol formula ; 

 a mixture of sandarac, camsal, and propylic alcohol, n = 

 1-478. 



(2) Camsal balsam, isobutylic alcohol formula, n = 1'485. 



(3) Euparal, a mixture of camsal, sandarac, eucalyptol, and 

 paraldehyde, n = 1*483. There are two sorts of this, the 

 colourless and the green (" euparal vert"), the latter con- 

 taining a salt of copper, which intensifies Jt sematoxylin 

 stains. 



Objects may be prepared for mounting in camsal balsam 

 by a bath of propylic or isobutylic alcohol ; and for euparal 

 by a bath of the special solvent (supplied by Griibler & 

 Hollborn under the name of " essence d'euparal "). But this 

 is not necessary. Objects may always be mounted direct 

 from absolute alcohol, and even at a pinch from alcohol of 70 

 per cent. I myself generally prefer alcohol of 95 per cent, 

 (absolute is dangerously volatile for sections). In difficult 

 cases you may pass through a mixture of the medium and 

 the solvent. 



These media work very kindly, and do not dry too rapidly. 

 They are not ( aidant, and preserve delicate stains (perfectly, 

 so far as I know). The mounts seem to keep perfectly, 

 without scaling : all of mine, the oldest being eight years 

 old, have kept without the slightest deterioration in any 

 r espect. 



The primary intention of these media is to spare delicate 

 objects the usual treatment with absolute alcohol and 



