86 Dr J. H. Gladstone on some Substances 



minous appearance present itself (as in the case of bisulphate 

 of quinine) beyond. The peculiar phenomenon of the blue 

 coloration of the liquid itself to a certain depth was exhibited 

 about the least refrangible portion of the ordinary blue ray. 

 I should have defined these positions by a reference to Fraun- 

 hofer's fixed lines ; but the atmosphere was too hazy at this 

 season of the year to admit of my obtaining a sufficiently good 

 and bright spectrum by means that exhibited the lines plainly 

 enough in the summer. 



Meconate of Iron. — The red solution that results when a 

 salt of the scsquioxide of iron is added to meconic acid, ex- 

 hibits on its surface a faint fluorescence. It showed itself 

 when the red was produced by double decomposition from the 

 ferric, nitrate, sulphate, or chloride ; but I failed to detect it 

 in the red solution that ensues when sesquioxide of iron itself 

 is dissolved in meconic acid. I believe this arises from the 

 meconate thus produced being a more acid compound ; for 

 there are several meconates A sesquioxide of iron, and I found 

 that the iron salt should be in excess to cause the blue, while 

 the addition of a large excess of meconic acid to a fluorescent 

 red solution will cause the appearance to cease. 



The blue in this case also seemed to be partially due to 

 opalescence ; but it was diminished in a marked manner when 

 a solution of bisulphate of quinine was interposed in the in- 

 cident ray. When placed behind a screen of ammoniacal 

 sulphate of copper, it displayed an intense blue ; but when 

 held behind one of ferrocyanide of iron dissolved in oxalic 

 aci !, scarcely any blue was perceptible. 



This meconate was found to transmit none of the rays of 

 the prismatic spectrum excepting the red and orange, and the 

 fluorescence in this case appeared to manifest itself about the 

 region where the green passes into the blue. 



Gallate of Iron. — A very faint fluorescence is exhibited by 

 the greenish-black solution that ensues when gallic acid is 

 added to a salt of sesquioxide of iron perfectly free from prot- 

 oxide. The blue fluorescence appears to be unaffected by an 

 excess of either the metallic salt or the acid. 



Platinum Salt. — If dilute solutions of bichloride of pla- 

 tinum and of iodide of potassium be mixed together in the pro- 



