^212 Dr. Schunck on Colouring Matters. 



The baryta compound gave the following : — 

 0'2i50 grm. gave 0*1420 sulphate of baryta, equivalent to 0*0932 

 baryta. 



Assuming that the formula of this compound is similar to that of 

 the last, viz. C,4 H4 O3 + BaO + HO, its composition would be as 

 follows : — 



Calculated. Found. 



1 eq. Alizarine 112 56*65 



1 „ Water 9 4*57 



1 „ Baryta 76*68 38*78 38*03 



197-68 100-00 



Neither of these compounds loses the equivalent of water which it 

 contains on being heated in a water-bath for several hours. 



The composition of crystallized alizarine must therefore be as fol- 

 lows : — 



Calculated. 



14 eqs. Carbon 84 56*75 



8 „ Hydrogen 8 5*40 



7 „ Oxygen 56 37*85 



148 100*00 



or, Calculated ^°"°/*- 



Numbers. 



II. 



1 eq. dry Alizarine. . . . 121 8176 



3 eqs. Water 27 18*24 18*33 18-32 



148 00*00 

 It follows that alizarine dried at 212° must consist of — 



Calculated. 



14 eqs. Carbon 84 69*42 



5 „ Hydrogen 5 4*13 



4 „ Oxygen 32 26*45 



121 100*00 



If this be the true composition of alizarine, it follows that there 

 exists a very singular relation between it and the composition of 

 benzoic acid. The formula of benzoic acid is C,4 Hg O4, and ali- 

 zarine only differs from it therefore by containing one equivalent less 

 of hydrogen. If we compare alizarine with isatine, we shall find 

 that the latter only differs from the former by containing in addition 

 the elements of one equivalent of cyanogen. The formula of isatine 

 is C16 H5 NO4 = C,4 H5 O4 4- C2 N. Anthranilic acid differs in 

 composition from alizarine in containing in addition the elements of 

 amidogene,for theformula of anthranilic acidisC,4H7N04=C,4 H5O4 

 + NH^. 



Alizar'ic Acid. — In my former report I stated that alizarine, when 

 treated with concentrated solutions of persalts of iron, is converted 

 into a new acid, which I called alizaric acid. I stated at the same 



♦ See pp. 210,211. 



