1880.] Modifications of the Spectrum of Potassium, Sfc. 281 



obtained from 1 grm. of " protagon " a residue of O0278 grm. of 

 metaphosphoric acid, but according to his spectroscopic estimate, less 

 than mgrm. of potassinm. What is the value of the latter half of 

 this statement when taken with the context of the other half? 



Before Professor Roscoe conld possibly obtain from snch a substance 

 as he seems to have examined any spectroscopic evidence of the 

 presence of potassium, he would have had to drive away from his 

 platinum wire a relatively enormous amount of free phosphoric acid. 

 He would then have had some potassic phosphate left, which, as we 

 have seen, gives only a feeble and indistinct potassium band in the 

 red, even when a large bead is heated in the flame before the spectro- 

 scope, and which, in so extremely small an amount as he must have 

 had, would of necessity give a fallaciously weak reaction. 



Further, Professor Roscoe seems not only to have thus overlooked 

 the inhibitive or weakening influence of phosphoric acid in relation 

 to the spectrum of potassium, but has also omitted to give any objec- 

 tive measures of the intensities which he purports to compare, has 

 moreover not recorded the length of time during which the compared 

 phenomena continued, and has not even named what was the 

 particular potassic salt used by him as a standard in his comparison. 



Aparb, therefore, from the inherently small worth of spectroscopy as. a 

 quantitative method, not even those precautions of which the spectro- 

 scopic method admitted were employed by Professor Roscoe, and I 

 must therefore respectfully submit my opinion that his experiment is 

 of no practical value. 



2. On the Inorganic Bases and Salts which are found, in combination with 

 the Educts of the Brain. 



Fremy, in his research on the brain published in 1841, stated that 

 the body which he had isolated and termed " cerebric acid," was 

 frequently combined with soda and phosphate of lime. Another sub- 

 stance, which he termed " oleophosphoric acid," he assumed to be 

 ordinarily in the state of soda salt, but sometimes, combined in part 

 with phosphate of lime. He separated these bases and salts by dis- 

 solving the mixture of the two bodies (cerebric and oleophosphoric 

 acid) in boiling absolute alcohol, which had been made slightly acid 

 by sulphuric acid. Sulphates of lime and soda remained suspended 

 mixed with some insoluble organic matter, and were removed by 

 filtration. The cerebric and oleophosphoric acids were in solution, 

 and deposited on cooling. From the mixture oleophosphoric acid was 

 extracted by ether, which left the cerebric acid behind. Fremy further 

 found that cerebric acid combined with all bases, and must be con- 

 sidered a true acid. When heated with dilute solutions of potash, 

 soda, or ammonia it did not dissolve, but combined with each of these 

 bases. The compounds were also obtained by mixing any of these 



