438 ALBUMINOUS COMPOUNDS. 



as fibrin, for a long time with water, especially under pressure, 

 in a Papin's digester, in a sealed glass tube, or in a soda-water 

 bottle. By boiling with dilute sulphuric acid or concentrated 

 hydrochloric acid, they are produced in a shorter time. The 

 production of peptones by the digestive ferments will be con- 

 sidered afterwards. 



35. Leucine. Preparation. It may be obtained by boil- 

 ing fibrin with dilute acid for a long time, or by digesting it 

 with pancreas, but it is more usually got from horn chips. 

 Hoil two parts of horn shavings with live parts of sulphuric 

 acid, previously diluted with thirteen parts of water, for twenty- 

 four hours, loss of water by evaporation being prevented by 

 the arrangement shown in 'fig. 329. Saturate the fluid while 

 hot, with chalk, filter, evaporate the filtrate to half its bulk, add 

 oxalic acid to precipitate the lime, filter and evaporate till a 

 scum forms on the surface, and then set it aside to crystallize. 

 A considerable amount of tyrosine will crystallize out first. 

 Pour off the liquor, let it stand till crystals of leucine form. 

 Purify them by boiling with water and lead hydrate, filter, re- 

 move'the lead by sulphuretted hydrogen, filter, evaporate the 

 filtrate in a water-bath to dryness: dissolve the residue in hot 

 weak alcohol, and let it cool and evaporate till crystallization 

 takes place. 



Leucine can be formed synthetically, and if wanted pure, 

 this is the best way of obtaining it. 



For this purpose a mixture of valeral-ammonia, hydrocyanic 

 and hydrochloric acids arc boiled together in a retort till the 

 oily ammonium compound has disappeared. The liquid is then 

 evaporated to dryness, the residue is boiled with water and 

 lead hydrate, and the product purified as already directed. 



Character.*. Leucine forms extremely slender, white, glisten- 

 ing plates. Allow a drop of a solution in water or alcohol to 

 evaporate on an object-glass and examine it under the micro- 

 It will form round balls, which are either hyaline, and 

 strongly resemble fat globules, or exhibit radiating lines. Or 

 it may appear as very thin plates grouped in a radiating fashion. 

 They differ from unites presenting a similar form in not being 

 strongly refractive. 



Siifiihilifi/. 1. Water: Pure leucine dissolves slowly, and is 

 soluble in about twenty-seven parts of cold water. It dissolves 

 more easily in hot water. AVhen impure it is more easily solu- 

 ble. 



J. Alcohol: Pure leucine dissolves in 1040 parts of cold, 

 and in 800 of hot alcohol. If impure, it is much more soluble. 



.".. In Liquor potassw, 4, ammonia, and 5, dilute acids, it is 



readily soluble. 



'.. Concentrated hydrochloric or sulphuric acids. It is dis- 



