1879.] ^15 [Smith. 



ance of the beautiful purple color, which is produced when salicylic acid 

 is brought in contact with ferric salts in solution. The best quantitative 

 filter paper invariably gave a deep purple coloration, and as the paper was 

 considered pure enough for all analytical purposes, a few tests were finally 

 made with a view of learning approximately the amount of iron which 

 could be detected by means of salicylic acid. As the halogeu substitution 

 derivatives of the acid give purple color with ferric salts several of them 

 were also experimented upon with the results recorded below. 



A litre of water containing one grain of iron as chloride was employed 

 in the preparation of the iron solutions. 



Salicylic Acid and Iron Solution. 



(1) The xoVo tn °f a S rm °f i ron — m a drop or two of water — gave a 



distinct violet color, when mixed with as much sali- 

 cylic acid as could be taken upon the end of a small 

 knife blade. The acid was usually dissolved in three 

 or four drops of alcohol. In the following tests the 

 same quantity of acid as above was used. 



(2) The 4o:ooo tn °f a S rm °f i ron — treated as in (1) gave distinct pur- 



ple coloration. 



(3) The soTffuo^ 1 °f a S rm °f n ' on — same as (2). 



(4) The so oto oo^ " " — decided purple color. 



(5) The ^ootVoo^ 1 " — distinct purple color. 



(6) The 372007000th " " — visible color. 



(7) The arrooVTooo^ 1 " " — very faint coloration. 



MetacMorsalicylic Acid (Fuses at 173°C.) and Iron Solution. 



(1) The T^vjoot' 1 0I " a S rm °f iron — beautiful purple color. 



(2) The sTrnhnyth " " — deep purple. 



(3) The ^ooTooot' 1 " " — faint purple color. 



(4) The ^oorooo 1 ^ " " — feint purple color, but more distinct 



than that produced by ordinary sali- 

 cylic acid. 



(5) The tts-o^ooo^ 1 " " — vei T faint color. 



Dibromsalicylic Acid (Fuses at 218°C.) and Iron Solution. 



The 4orooo tu °f a S rm °f i r011 — remarkably deep purple color. 

 The so7ooo tu " — ver y deep purple color. 



The T g oto oo th " — distinct purple color. 



The 177100-70 oo ta " " — barely visible color. 



Upon adding a drop of a potassium sulphocyanide solution to one con- 

 taining the g^oVoroooth °^ a ^ rm " °^ * rou a c ^ stmct re< ^ color was noticed. 

 Farther tests were not made. 



I noticed, however, that salicylic acid was a decidedly good reagent for 

 iron in the presence of an excess of copper. In fact it is more delicate 

 than sulphocyanide in such cases. 



Laboratory of the University of Pennsylvania, March 21, 1879. 



