138 INORGANIC AGENTS 



odor or taste. Permanent in air. Insoluble in water or alcohol. Used only exter- 

 nally. 



Plvmbi Nitbas. Lead Nitrate. Pb (NOs)^. (Non-official.) 



Synonym.— Flumbnm nitricum, azotate (nitrate) de plomb, Fr.; salpeter- 

 saures bleioxyd, bleisalpeter, G. 



Derivation. — Dissolve lead in nitric acid. 



Properties. — Colorless, transparent, octohedral crystals, or white, nearly 

 opaque crystals; without odor, and having a sweetish, astringent, and afterwards 

 metallic taste; permanent in the air; reaction acid; soluble in' 1.85 parts of water; 

 almost insoluble in alcohol. Only used externally in 1 per cent, solution as an 

 astringent and deodorant in gangrenous surfaces, etc. 



Plumbi loDmuM. Lead Iodide. Pb I2. (Non-official.) 



Synonym. — Plumbum iodatum, iodure de plomb, Fr.; jodblei, G. 



Derivation. — Treat solution of lead nitrate with that of potassium iodide. 



Pb (N03)2-|-2 KI=Pbl2+2 KNO3. Dry the precipitate. 



Properties. — A heavy, bright, yellow powder, without odor or taste; perma- 

 nent in the air; soluble in about 1,300 parts of water; very slightly soluble in 

 alcohol; used only externally. 



PREPARATION. 



Unguentum Plumbi lodidi. Ointment of Lead Iodide. (B. P.) Employed 

 externally to absorb glandular swellings. 



Action of Lead Salts. 



External. — Soluble lead salts differ somewhat from salts of the other 

 heavy metals in being more astringent and less irritant. This happens 

 because they form a denser precipitate with albumin of the tissues and 

 of secretions. The acetate which is generally used is dissociated slowly 

 in solution in contact with the tissues. The metallic ion coagulates albu- 

 min by forming a lead albuminate^ so producing a protective pellicle over 

 raw surfaces ; while the acid constituent has little effect (lack of irrita- 

 tion). The acetate thus makes the tissues drier, denser and harder — and 

 contracts vessels — but has no action on the unbroken skin. 



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, probably a soluble albuminate. Lead is deposited in the 

 tissues, especially in the liver and kidney, and is very slowly eliminated 

 in the urine and intestinal mucus, bile, milk and saliva. Lead salts have 

 a marked astringent action on the entire digestive canal and diminish 

 secretions accordingly. After absorption lead salts have no remote astrin- 

 gent action. 



Toxicology. — Poisoning not infrequently occurs in animals at pas- 

 ture, from eating paint, sheet lead, or products of lead or smelting 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 sulphate is deposited upon the interior of the pipes. There is an 

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

 doses of soluble lead salts, and is characterized by gastro-enteritis and , 

 colic; rarely there are symptoms of absorption, as convulsions, coma, 

 paralysis and death. The feces are sometimes colored black with lead 



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