HORNS, NAILS, AND SCALES. 307 



composition, so that it can be squeezed into a mould and wrought 

 into various forms, as is well known. When horns are distilled 

 per se they give out a great quantity of fetid oil, a little carbo- 

 nate of ammonia, together with a minute quantity of water. The 

 charcoal remaining in the retort amounts to about one-sixth of 

 the weight of the horns distilled. It has a semi-metallic lustre, 

 and when burnt leaves a quantity of white ashes constituting 

 about half a per cent, of the weight of the horns. It consists of 

 phosphate of lime with a little carbonate of lime and phosphate 

 of soda. 



Horn is insoluble in water ; but when boiled for several days 

 in that liquid, it is softened, and the water is slightly precipitated 

 by chloride of tin, but not by tannin. When horn is strongly 

 heated with water in a Papin's digester, it is said to be convert- 

 ed into a gelatinous mass which possesses the properties of gela- 

 tin. Horn is insoluble in alcohol and ether. These liquids, how- 

 ever, separate a small quantity of fatty matter. 



Concentrated sulphuric acid, at the temperature of 57, does 

 not dissolve horn nor acquire any colour from it. But the horn 

 is softened by the acid. If we wash it with water, and then boil 

 it in that liquid, a portion of it is dissolved, and the liquid is pre- 

 cipitated by corrosive sublimate and infusion of nut-galls. Di- 

 lute nitric acid softens horn ; but a long maceration is required 

 before this effect is produced. If we pour ammonia on the sof- 

 tened horn it becomes first reddish-yellow, then blood-red, and 

 finally dissolves into a dark -yellowish red liquor. If we wash 

 horn softened by nitric acid with cold water, and then boil it in 

 a new quantity of water, it dissolves, forming a yellow liquid, 

 which gelatinizes on cooling. This jelly is dissolved by cold 

 water, and the solution is precipitated by tannin. Concentrated 

 nitric acid dissolves horn. If we evaporate the solution to dry- 

 ness, it detonates. Horn is not softened when macerated in 

 concentrated acetic acid. But when it is digested for some days 

 in a close vessel in dilute acetic acid, that liquid dissolves a portion 

 of it without becoming coloured, and when the liquid is evapo- 

 rated to dryness, a light-yellow substance remains, which is tran- 

 sparent, and not soluble in water. 



If, after freeing horn from fat by means of alcohol, we dry it, 

 and pour over it concentrated muriatic acid, after an interval of 

 a day or two it becomes blue, though the acid acquires no colour, 



