232 LEAD OXIDES AND CARBONATE 



phates, or phosphates, are less liable to contamination, as 

 their acid, uniting with the lead, forms an insoluble crust, 

 which protects the metal from further action of air or water. 

 But even such hard waters are not absolutely safe from lead 

 contamination. A piece of iron, a patch of soft solder, or a 

 few carbonaceous or other impurities in the lead, are liable 

 to set up galvanic action, and thus dissolve the metal. 

 Great care should therefore be taken to prevent lime, mortar, 

 nails, or in fact any foreign body, getting into leaden 

 cisterns, which should further be emptied and cleaned out 

 frequently, especially when new. 



In acute poisoning an emetic or the stomach pump is 

 promptly used, followed by a soluble sulphate, such as 

 magnesium sulphate, to form the insoluble lead sulphate, 

 then by demulcents, such as albumin, oils, gruel, etc., and 

 appropriate agents to combat the collapse. In chronic 

 poisoning, the lead, whether deposited in the tissues or 

 lodged in the digestive canal, should be excreted as rapidly 

 as possible. If in the intestine, by the action of mag- 

 nesium sulphate, and if in the tissues, by means of potassium 

 iodide. This agent is believed to combine with the lead 

 albuminate in the tissues, forming the more readily excreted 

 lead iodide, which is removed by the kidneys. Diuretics 

 should be given at the same time, and a nutritious 

 strengthening diet. 



LEAD OXIDE. Plumbi Oxidum. Litharge. 



LEAD CARBONATE. Plumbi Carbonas. White Lead. 



There are five oxides of lead. Litharge (PbO) is a yellow- 

 ish-red, scaly powder, prepared by the action of air on melted 

 lead. 



Lead carbonate, or white lead, may be prepared by the 

 interaction of lead, water, and carbonic anhydride, in the 

 presence of vapours of acetic acid (B.P.). It is insoluble in 

 water ; entirely soluble in diluted acetic acid. 



ACTIONS AND USES. Litharge and white lead are used topi- 

 cally as desiccants and astringents. Mixed with linseed oil, 

 glycerin, or vaseline, they form antiseptic, astringent, pro- 

 tective coverings, useful in burns, herpes, and moist eczema. 



