l\Q ON LARD, AND COMPOUNDS MADE WITH IT. 



pounds more or less in use, as the mercurial piaster of Vigo, 

 ethiops saccharatiis, ethiops alkalisatus, Plenck's gummy 

 mercurial, aud a number of s'.milar mixtures. If the colour 

 be objected, it may be observed, that antimony, however 

 brilliant, bismuth, or any other metal capiible of being pow- 

 dered, becomes of a blackish gray when minutely divided. 

 Action on salfs. Mr. Vo^el next examined the action of fat on metallic 



salts. 



Ointment of He prepared the unguentum citrhmm by dissolving three 



Hlve^r.^^^"*^^' ounces of mercury in four of uitric acid, and mixing them 



with two pounds of lard. As the surface of this ointment 



always grows white after a time, for wliieh some account by 



ascribing it gratuitously to the absopption of oxigeu by the 



air, he poured this ointment while still fluid into squares of 



paper. Some of these he' placed under a jar filled with air 



over mercury. Tn twenty-four, hours no absorption had 



taken place, yet the surface was strikingly whitened. Others 



he placed under the receiver of an airpump, in which he 



speedily made a vacuum ; and. this he kept up for some 



hours, giving occasionally a stroke with the p'ston, which at 



lirst occasioned an ebullition of air-bubbles. The ointment 



. when removed from the vacuum was perfectly yellow, and 



remained in this state without the least change. 



Whiteness of From these experiments he conceives, that the white crust 



the surface ow- jg owing" to the extrication of gas, either nitrogen or nitrous, 



ing to air (le- .... „ ,, i • i ^ ^ i /• ' ■ ■, 



taineJ there, which arrives rrom all the internal parts at the surtace, and 



increases its volume. As it gradually cools, it does not l^ave 



the gas time to escape entirely, so that part of it remains, 



and forms an infiuite number of small white bubbles at the 



surface. ' . i*^ 



Mavbemade i^^ confirmation of this may be added,- that, when the 



so as to remain ointment is suiiered to cool in the vessel in which it was kept 



^ ' in fusion, and |5articularly when it is still heated a little, 



the quantity of caloric is sufficient to expel all the gas, and 



the ointment remai^ns constantly yellow, without undergoing 



any farther alteration.. 



„ ., ■ To examine this compound, and form a judgment of the 



Boilca in wa- jo 



ttr. chemical changes, that might have taken place, Mr. Vogel 



bojled in water for half an hour some ointment, that had 



been made about two years* It became very clotty, and the 



water 



