1880.] 



On the Absence of Potassium in Protagon. 



365 



at 22 indies from the centre of the shoulder joint, we obtain for the 

 value of a, 



a=5'56 lbs. + 0'125 (probable error). 



This result agrees remarkably well with the result «=5*681bs., 

 obtained by calculations founded on the Law of Fatigue, from the 

 long series of observations detailed in this note. 



V. " On the Absence of Potassium in Protagon prepared by 

 Dr. Gamgee." By H. E. Roscoe, LL.D., F.R.S. Received 

 April 29, 1880. 



Protagon is stated by Gamgee to contain no potassium. Thudichum, 

 on the other hand, asserts that this body contains from 0'7 to 1*6 per 

 cent, of this metal. 



In order to ascertain the quantity of potassium contained in pro- 

 tagon prepared by Gamgee, 5 grams of this material was completely 

 burnt, leaving a residue of 0*177 gram, consisting chiefly of meta- 

 phosphoric acid. On precipitating the potassium in the usual way, 

 and on decomposing the platinochloride, a residue of 0*003 gram of 

 platinum was obtained ; this corresponds to a percentage of 0'0236 of 

 potassium on the protagon employed. 



Spectroscopic experiments, made upon solutions of the chloride and 

 phosphate of potassium, and upon a solution of the latter salt with the 

 addition of the relative quantity of phosphoric acid present in the ash, 

 according to the above analysis, convinced me of the correctness of 

 the conclusions contained in my letter printed on page 113, vol. 30, 

 of the "Proceedings of the Royal Society." 



The Society adjourned over Ascension Day to Thursday, May 13. 



Presents, April 8, 1880. 



Transactions. 



Amsterdam : — K. Akademie van Wetenschappen. Verhandelingen. 

 Deel XIX.' Afdeeling Letterkunde. Deel XII. 4to. Am- 

 sterdam 1879. Verslagen en Mededeelingen. Afdeeling Natu- 

 urkunde. Tweede Reeks. Deel XIV. Afdeeling Letterkunde. 

 Tweede Reeks. Deel VIII. 8vo. Amsterdam 1879. Jaarboek, 

 1878. 8vo. Processen-Verbaal, Afdeeling Natuurkunde, 

 1878-9. 8vo. Elegiee Duee. 8vo. Amstelodami 1879. 



The Academy. 



