LEAD OLEATE AND IODIDE 233 



Animals, however, are prone to eat or lick such dressings, 

 and to obviate risk of poisoning, zinc oxide and carbonate 

 are hence usually substituted. 



LEAD OLEATE. Lead Plaster. Emplastrum Plumbi. 



The common sticking or diachylon plaster is prepared by 

 boiling together gently, by the heat of a steam bath, one 

 pound litharge, two pounds olive oil, and sixteen ounces of 

 water, keeping them simmering for four or five hours, stirring 

 constantly until the product acquires a proper consistence 

 for a plaster, and adding more water if necessary (B.P.). 

 In this process the oil is decomposed in the same manner 

 as fats are acted upon by steam heat, or by alkalies in the 

 preparation of soap ; lead oleate rises to the surface, and 

 glycerin remains in solution. Lead plaster is sold in rolls, 

 about a foot in length, of a yellow-white colour, and a 

 faint, sweet, soapy odour. Although brittle when cold it 

 becomes soft and adhesive when heated. 



ACTIONS AND USES. Lead plaster is adhesive, free from 

 irritant properties, and the lead is not liable to absorption. 

 For bringing together the edges of small incised wounds it 

 is generally used spread on linen or calico, and thus applied 

 it besides affords protection and support. Lead plasters are 

 rendered more adhesive, and consequently better adapted 

 for most veterinary purposes, by melting with every pound 

 four ounces of pitch or resin and two ounces of hard 

 soap. 



LEAD IODIDE. Plumbi lodidum. PbI 2 . 



When equal parts of lead nitrate and potassium iodide 

 are dissolved, and the solutions mixed, double decomposi- 

 tion occurs, potassium nitrate remains in solution, and lead 

 iodide is precipitated in brilliant, golden-yellow, crystalline 

 scales, or in a fine, bright yellow, heavy powder. It is taste- 

 less, colourless, sparingly soluble in cold water, but readily 

 dissolved by 200 parts boiling water, entirely soluble in 

 solution of ammonium chloride. 



ACTIONS AND USES. It resembles other lead salts ; is occa- 



