IX, A, 2 Pratt and Brill: Phthalide Compounds 123 



In a like manner, the introduction of a metal atom in thio- 

 phthaloxime gives a maximum reciprocal effect, represented 

 by the formula: 



C= S _ 



C=NO/ 



The heavy dots between sulphur and metal may serve to in- 

 dicate that the equilibrium of partial valency is emphasized in 

 the salt, while the corresponding light dots show the lesser 

 importance of conjugation in the oxime. 



The color and selective absorption of thiophthaloxime cannot 

 be explained by molecular rearrangement. The compound still 

 contains a hydroxyl group capable of giving an acetate with 

 acetic anhydride. The acetate is orange, but gives an absorption 

 spectrum containing no color band. Its color is due entirely to 

 general absorption, and the reason that this cuts into the visible 

 region while that of phthaloxime acetate is much farther toward 

 the shorter wave lengths at corresponding concentrations is to 

 be attributed to the greater activity of the lactone ring contain- 

 ing sulphur. The structure of the acetate, therefore, is correctly 

 represented by the formula: 



C=S 

 >0 

 C=N0C0CH3 



C6H4<^^( 



The molecular arrangement of the acetate must be identical 

 with that of the oxime as the ultra-violet bands of both sub- 

 stances are identical (fig. 6). 



All of these relationships taken together conclusively show 

 that the spatial arrangement of the molecules of phthaloxime, 

 its salts, ethers, and esters, and of the corresponding thiophthal- 

 oxime compounds is the same in each case. No rearrangement of 

 the molecule takes place upon salt formation, and the production 

 or variation of color must be dependent upon changes in con- 

 jugation between partial valencies. 



Thiophthaloxime dissolved in concentrated sulphuric acid gave 

 a much simpler absorption spectrum (fig. 5). Since the sul- 

 phate was isolated from this solution, the spectrum doubtless 

 represents the combination of oxime and acid. Such an addition 

 product must not be confused with the type of conjugated com- 

 bination postulated for such a substance as phthalophenone in 



