286 Modifications of the Spectrum of Potassium. [Mar. 18, 



principal ammonium base from the phosphorised substances has, after 

 purification by the phosphomolybdic process and combination with 

 hydrochloric acid and platinic chloride, invariably the composition 

 C 5 H 13 NO. 



The stoichiometric relations of such a base, in its platinic chloride 

 salt, would be doubly disturbed by the presence of potassium ; for not 

 only would a portion of the platinic chloride, namely that combined 

 with potassic chloride, be erroneously referred to neurin, but the entire 

 amount of platinum, if estimated, as is usual by combustion, would be 

 raised in apparent amount by the presence of the potassic chloride as 

 an invisible impurity. 



The Albuminous Ingredient of the brain contains considerable 

 amounts of the usual salts, particularly calcic phosphate, of which the 

 calcium is obtained as gypsum, when the albumin is treated with dilute 

 sulphuric acid, and the solution of hemi-albumin is filtered from the 

 undissolved hemi-prote'iu and slowly evaporated. By combustion of 

 the albuminous matter of the brain, all the usual salts and bases, 

 including copper, iron, and manganese, are liberated. 



The greater part of the soluble salts contained in the brain passes 

 into the water extracts, while the greater part of the insoluble salts, 

 such as phosphates of earths, remain with the albumin ; but a portion 

 of both remains with the phosphorised and nitrogenised principles, and 

 follows them into all their solutions in ether and alcohol. Only sulphates 

 have not been found in these latter, though they are present in the 

 water extracts. 



It follows that all educts from the brain have to be freed from the 

 salts or bases described before they can be subjected to quantitative 

 chemical examination ; and an error which seems to me to pervade all 

 analyses of the brain for inorganic ingredients hitherto is the follow- 

 ing. When the brain is burnt in its entirety, the phosphoric acid 

 resulting from the destruction of the phosphorised compounds expels 

 sulphuric, hydrochloiic, and carbonic acids, and comes to be considered 

 as an inorganic ingredient, the fact of its previous combination being 

 overlooked. When the brain is freed from matter soluble in spirit 

 and ether, and the albumin and water extract alone are examined for 

 inorganic ingredients, the fallacy otherwise introduced by the phos- 

 phoric acid in organic combination is no doubt avoided ; but the inor- 

 ganic salts described above, as in combination with the phosphorised 

 and nitrogenised matters are overlooked and left out of consideration. 



A vast range of other organic analyses (animal and vegetable) for 

 inorganic constituents is no doubt affected by the same fallacy, and it 

 seems to me that the right making of such analyses is a much more 

 complicated problem than has hitherto been believed. 



