ACTION OF LEAD SALTS 163 



Pb (NO3), + 2 KI == Pbl, + 2 KNO3. Dry the pre- 

 cipitate. 



Properties. — A heavy, bright yellow powder, without 

 odor or taste ; permanent in the air ; soluble in about 2,000 

 parts of water ; very slightly soluble in alcohol ; used only 

 externally. 



PREPARATION. 



Unguentum Ptumhi Todidi. Ointment of Lead Iodide. (U. S. & B. P.) 



Lead iodide, 10; oenzoinated lard, 90. Employed externally to 

 absorb glandular swellings. 



ACTION OF LEAD SALTS. 



External, — Lead salts act like other astringents in con- 

 tracting tissues and vessels, and in coagulating albumin of 

 exudations, but unlike these agents generally, they are 

 sedatives and not irritants locally. 



Internal. — Soluble salts of lead in concentrated solution 

 — and at times insoluble salts— cause gastro-enteritis in 

 large doses. Lead salts are absorbed in medicinal doses 

 whether taken in a soluble or insoluble state. The chemical 

 form of the lead compound at the time of absorption is 

 unknown. Lead is deposited in the tissues and very slowly 

 eliminated in the urine and intestinal mucus. Lead salts 

 have a marked astringent action on the entire digestive 

 canal and diminish secretions accordingly. It is doubtful 

 whether lead salts remotely contract blood vessels after 

 absorption. There are other agents — notably ergot — which 

 possess much greater power for this purpose. 



Toxicology. — Poisoning not infrequently occurs in animals 

 at pasture, from eating paint, sheet lead, or products of lead 

 works. The drinking water may be contaminated with lead, 

 especially from new pipes, or lead receptacles in which 

 water has been standing. Hard water is not affected by lead 

 pipes, since an insoluble crust of lead phosphate and sulph- 

 ate is deposited upon the interior of the pipes. There is an 

 acute and chronic form of poisoning. The first is caused by 



