IX, A, 2 Pratt and Brill: Phthalide Compounds 115 



Thiophthaloxime dissolves in concentrated sulphuric acid solu- 

 tion with a yellow color. The absorption spectrum of such a 

 solution showed no band in the visible region. The color is, 

 therefore, due to general absorption. The small band in the 



ultra-violet was shifted to - = 2880, and the persistence of the 



1 

 band heading at - = 3480 was reduced, 



A 



THIOPHTHALOXIME SULPHATE 



c=s 



C6H4<^0 



C=NOH-H2S04 



Thiophthaloxime dissolves in concentrated sulphuric acid to 

 form a sulphate that may be obtained by pouring the solution 

 into an excess of ice water. The sulphate slowly crystallizes 

 out in long yellow needles on standing. Recrystallized from 

 dry benzol, it was obtained in stout yellow prisms melting with 

 slight decomposition at 159° (corrected). 



The sulphate is soluble in absolute alcohol with a yellow 

 color. Upon the addition of water and boiling, the solution 

 turns red, showing the splitting off of sulphuric acid and 

 regeneration of thiophthaloxime. The solution in absolute 



alcohol gave an absorption spectrum with bands at - = 3100 



1 ^ 



and - = 3700. General transmission extends into the ultra- 



A 



violet a much greater extent than with the free oxime (fig. 5, 

 page 116). 



The metallic salts of thiophthaloxime are highly colored, those 

 of ammonia and the alkali metals being purple. They are very 

 unstable in the presence of moisture, and rapidly go over into 

 colorless salts of thiophthalhydroxamic acid. 



c/ 



C6H4<^'\OH 

 C=NOH 



An aqueous solution of the sodium salt became colorless 

 almost immediately, and gave a reddish purple color with ferric 

 chloride, showing the presence in the colorless solution of 

 hydroxamic acid. The sodium salt may be obtained by adding 



