118 Staining Procedures (chap. 11) 



(Gejieral Biological Supply House) with a refractive index of 1.51 to 

 1.52. Hartman-Laddon Company sells "HRS," Harleco Synthetic Resin, 

 index of refraction 1.5202; Will Corporation has a Bioloid Synthetic 

 Resin, index of refraction 1.5396; Ward's sells Kleermount; also the 

 Technicon Company sells one. The resins should have refractive indices 

 of 1.53 to 1.54 or better. (Lillie et al., 1953) There is no reason to 

 recommend one of the above products over the others; all are equally 

 efficient. They are soluble in xylene, toluene, aromatic hydrocarbon 

 solvents, and in chlorinated hydrocarbons such as chloroform, but not 

 in Dioxane. 



Hyrax (Fisher Scientific Company), refractive index 1.71, is a perma- 

 nent, neutral synthetic naphthalene resin, formulated by Dr. G. Dallas 

 Hanna for mounting diatoms. It is good for some unstained botanical 

 and parasitological materials which lose detail in other synthetics be- 

 cause they become too clear. Hyrax brings out structure of colorless 

 fibers and spines. 



Lillie et al. (1950) recommend Lustron 2020 for good preservation of 

 Prussian blue mounts, which tend to fade in some resins. Lustron is a 

 polystyrene manufactured by Monsanto Chemical Corporation and has 

 a refractive index of 1.59. It is water resistant and soluble in varying 

 degrees in aromatic and chlorinated hydrocarbons. The above authors 

 used it in diethylbenzene as solvent. The present author has had excel- 

 lent results using toluene or xylene without the formation of air bays 

 as the xylene evaporated. If such trouble is encountered, diethylbenzene 

 is recommended; Lillie et al. suggest adding 5 ml. dibutylphthalate to 

 70 ml. xylene and 25 gm. polystyrene. This does not delay hardening. 



There are also the German synthetics, Caedax and Rhenohistol, and 

 the British ones — Xam, Cristalite and Clearmount. These are similar 

 in most respects to American products. 



Most synthetic moiuitants are allowed to air dry, but if quick drying 

 is a must, try this method of Manikas and Umiker (1939): After slides 

 are covered, place them on metal trays in a drying oven, 160-170°C, 3 

 minutes. Remove and chill in freezing compartment of refrigerator, 2 

 minutes. Slides can be cleaned, marked with ink and stored without 

 dislodging cover glasses. 



Aqueous mounting media are indispensible for the preservation of 

 tissue elements which are soluble in alcohol or hydrocarbons, or are 

 demonstrated by the use of dyes soluble in these fluids. A number of 

 media have been proposed using (1) gelatine and gum arabic as solidify- 

 ing agents with water, (2) sugars and salts for increasing the refracti\e 



