CORRODED PREPARATIONS. 391 



are vermilion, king's yellow, blue verditer and flake-white. Others may 

 be used. They are in general to be mixed with the injections when 

 melted ; but there are some exceptions to this rule, particularly with 

 regard to the verditer, and in some measure to the flake-white, for they 

 both unite (at least in part) with the injection chemically, and effer- 

 vesce ; to prevent which we find it necessary to melt some of the 

 ingredients alone, and add the colour to these before the others are 

 added. The following experiments will particularize these exceptions. 



1st. Blue verditer with tallow alone causes no fermentation. 2nd. 

 Blue verditer with wax alone does not ferment. 3rd. Blue verditer 

 with resin does ferment, therefore mix the verditer with the tallow or 

 wax either alone or together, and afterwards add the resin, which causes 

 a small fretting. If you use 01. Olivar. instead of tallow, use it in mixing 

 the colour as you did the tallow. If, instead of tallow, you use the 

 turpentine varnish or 01. Tereb., mix the colour first with the melted 

 wax ; then add either of those ingredients you intend to use, and then 

 the resin. These observations are equally applicable to the flake- white. 



When we make a white injection, instead of the yellow wax we use 

 the white ; it will not even then be of a good colour, unless we load the 

 injection, and make it pretty thick with the colour. It would seem 

 that we have not yet any good green colour ; but as blue and yellow 

 make a green, blue verditer, added to yellow wax or resin, gives us a 

 fine green. 



Treatment of Parts after being injected for Corrosion. — A part that is 

 injected for corrosion, whose figure alters by taking it out of the body, 

 should be put into its natural form when put into the acid, and into 

 such a vessel as is best adapted for such a figure. The distance of time 

 between the injecting and the putting it into the acid, should be just 

 when the injection has taken a solid form, which it will do sooner or 

 later in proportion to the size of the preparation. If it cannot be put 

 into the acid before the injection is quite cold (from the want of acid), 

 take care that you put it into the vessel it is to be corroded in, that it 

 may take the right shape, and afterwards you may add the acid ; but 

 if both these rules should be neglected, and it is allowed to cool in a 

 wrong position from its natural one, then it must be put into warm 

 water till the injection has acquired that degree of softness as to allow 

 the part to take its natural form in the vessel it is to be corroded in. 



When you inject a part for corrosion in the summer, you must put it 

 immediately into spirit of sea salt ; because it will soon beg-in to putrefy, 

 by which means the vessels will be either broken or bent by handling 

 afterwards. 



Of washing Parts after they are corroded. — After a part is sufficiently 



