ADVANCED PHYSIOLOGICAL CHEMISTRY 431 



are then mixed together, and 5 per cent, acetic acid added to the 

 combined extract till it becomes faintly acid in reaction. A dirty 

 white precipitate is produced, which is nucleo-albumin. In order 

 to purify it, the precipitate is collected on a filter paper and 

 redissolved in ammonia water, the nucleo-albumin being again 

 precipitated by the addition of acetic acid. In order to prepare 

 nuclein from this, the precipitate is transferred to a small beaker or 

 flask, and to it is added about ten times its bulk of O2 per cent, hydro- 

 chloric acid, and about 10 c.c. liquor pepticus. The mixture is placed in 

 the incubator at 37 C. for about 48 hours, after which time it will be 

 noticed that a considerable amount of the precipitate has dissolved, and 

 that a brownish sediment has fallen to the bottom of the vessel. This 

 sediment is nuclein, the albumin having gone into solution as peptone. 

 The nuclein is collected on a filter paper, and washed free of im- 

 purity by means of 0*2 per cent, hydrochloric acid. In order to further 

 purify it, the precipitate is dissolved in 0*5 per cent, ammonia water, 

 and the nuclein reprecipitated by the addition of 5 per cent, acetic acid. 

 From the above method of preparation it will be noticed that both 

 nucleo-albumin and nuclein are soluble in alkali, and insoluble in acid. 

 In this respect they agree with mucin, and frequently they are confused 

 with this body. They are distinguished from mucin, however, by the 

 fact that they contain phosphorus. This can be detected by fusing 

 some nuclein in a silver basin with potassium hydrate and potassium 

 nitrate. By so doing the organic matter is burnt off as carbonic acid 

 and ammonia, and the liberated phosphorus unites with the alkali to 

 form a salt. After cooling, the mass is dissolved in water, transferred 

 to a beaker, and made acid with nitric acid. 



The technique of the method is as follows : 



A weighed quantity of the organic substance (about 1 gr. nuclein) is placed in 

 a silver basin and about 10-12 times its weight of caustic soda (NaOH) and a 

 minute pinch of nitre (KN0 3 ) added to it. A small amount (2-3 c.cm.) of water 

 is then added, and the silver basin placed on a boiling water bath until a solid 

 cake has formed. The basin is then caught hold of by means of two pairs of 

 crucible tongs and held over a free flame till the cake melts, the basin being 

 meanwhile gently rotated so as to keep its contents in motion and thereby 

 prevent spirting. The heating is continued, a pinch of nitre being added about 

 every minute, until all the carbon, which soon separates out as black specks, 

 has been oxidised. Great care must be taken that the oxidation Is not too 

 rapid (i.e. the nitre must be cautiously added and the flame kept low), and the 

 basin must be continuously rotated to prevent spirting. 



When all the carbon has disappeared and the fuse ' has become colourless, 

 the basin is cooled, water added, and its contents carefully washed into a beaker 

 and the P determined by the usual gravimetric method. When burning a sub- 



