284 ANTISEPTIC PLASTERS. 



acid, 2 1 parts (by weight). Heat half the olive oil 

 over a slow fire, then add the litharge gradually, stir- 

 ring constantly till the mass becomes thick or a little 

 stiff; then add the other half of the oil, stirring as 

 before till it becomes again thick. Then add the wax 

 gradually till the liquid again thickens. Remove 

 from the fire, and add the acid, stirring briskly till 

 thoroughly mixed. Cover up close, and set aside 

 to allow all the residual litharge to settle ; then pour 

 off the fluid, and spread upon calico to the proper 

 thickness. The plaster made in this way can be spread 

 by machine and kept rolled in stock ; and, if in a well- 

 fitting tin canister, will retain its virtues for any length 

 of time. , 



Antiseptic Lac-Plaster. Shellac, 3 parts ; crystal- 

 lised carbolic acid, I part. Heat the lac, with about 

 one-third of the carbolic acid, over a slow fire till com- 

 pletely melted; then remove from the fire and add 

 the remainder of the acid, and stir briskly till the in- 

 gredients are thoroughly mixed ; strain through mus- 

 lin and pour into the machine for spreading plaster; 

 and, when the liquid is thickened by cooling to a degree 

 ascertained by experience, spread to the thickness of 

 about one-fiftieth of an inch. Afterwards brush over 

 the surface of the plaster lightly with a solution of 

 gutta percha in about 30 parts of bisulphide of carbon. 

 When the sulphide has all evaporated, the plaster 

 may be piled in suitable lengths in a tin box without 

 adhering, or rolled up in a canister. 



