Infiltration and Embedding in Paraffin Wax 35 



triangle in a pan, which serves as an air bath, heated by a small 

 Bunsen flame (Fig. 5.2) . 



Infiltration With Paraffin Wax 



The following infiltration procedure may be used with any of 

 the common sohents, if the respective specific gravities of the solvent 

 and the wax are taken into account. Paraffin wax, either in solid or 

 melted form, floats on chloroform and also on dioxan. Therefore, 

 either of these solvents, used alone, provides the progressive infiltra- 

 tion that will be emphasized in this chapter. The addition of chloro- 

 form or xylene to dioxan, as suggested previously, merely accelerates 

 the dissolving of the wax. 



Paraffin sinks in xylene, but if the melted wax is poured into a 

 bottle of cold xylene along the side of the bottle, a solidified layer 

 of wax will remain on top of the solvent during preliminary infiltra- 

 tion at 25 to 35°C. When the solvent is warmed above the melting 

 temperature of the wax, the nearly pure wax will sink to the bottom 

 and envelop the tissues. The abrupt concentration gradient between 



Fig. 5.2-Casting tables: A, boiler-plate table (the dotted line indicates the melting 



zone) ; B, warm-pan device. 



the wax and the tissues may be destructive to fine detail. The addition 

 of lOVt chloroform by volume to the much cheaper xylene raises 

 the specific gravity sufficiently to float wax chips or melted wax, and 

 a gradual downward diffusion gradient is obtained. 



Normal and tertiary butyl alcohol have a lower specific gravity 

 than paraffin wax, and the wax sinks upon the tissues. Flotation of 

 wax can be obtained by the addition of chloroform, 15% by volume 

 to normal butyl alcohol, and 25% to tertiary butyl alcohol, respec- 

 tively. If chloroform is not added, the addition of wax must be made 

 by small increments, in liquid form, and each increment must be 

 homogenized to prevent the added wax from sinking and enveloping 

 the tissues. 



