210 Dr. Schunck on Colouring Matters. 



Alizarine. — Concerning the properties of alizarine I have nothing 

 to add to what I stated in my last report, except that when crystal- 

 lized from alcohol it contains several atoms of water of crystalliza- 

 tion, which it loses when heated to 212° F. The crystals after being 

 heated to this point have not lost their shape, but have become 

 opake and of a much redder colour, resembling that of native 

 chromate of lead. On placing them in a tube immersed in a sul- 

 phuric-acid bath, and heating the bath, no further change takes place 

 until about 420° F., when a sublimate of orange-coloured crystals 

 begins to appear on the cold part of the tube. 



On subjecting alizarine to elementary analysis I obtained the 

 following results : — 



I. 0*3205 grm. of crystallized alizarine dried in theairgave,on being 

 burnt with chromate of lead, 0*6695 carbonic acid and 0*121 water. 



II. 0*3985 grm. of the same gave 0*8320 carbonic acid and 0*] 850 

 water. 



III. 0*3140 grm. gave 0*6565 carbonic acid and 0*1670 water. 

 These numbers correspond in 100 parts to — 



I. II. III. 



Carbon 56*97 56*94 57*02 



Hydrogen 4*19 5*13 5*87 



Oxygen 38*84 37*93 37*11 



100*00 100*00 100*00 



The great discrepancy in the amounts of hydrogen in the prece- 

 ding analyses arises from the circumstance that alizarine loses its 

 water of crystallization with such extreme facility. No. I. was mixed 

 with warm chromate of lead in a warm mortar ; No. II. was mixed 

 with warm chromate of lead in a cold mortar ; and No. III. with 

 cold chromate of lead in a cold mortar. In the case of No. I. there- 

 fore we see that the heat of the chromate of lead and the mortar 

 combined was sufficient to drive away more water than what corre- 

 sponds to 1^ per cent, of hydrogen, though this heat was not greater 

 than what might be borne by the hand. In order to determine the 

 amount of water of crystallization, crystallized alizarine was heated 

 in a water-bath until it lost no more in weight. 



I. 0*4015 grm. treated in this way lost 0*0735 water. 

 II. 0*3575 grm. lost 0*0655 water. 



Alizarine which had been deprived of its water of crystallization 

 by heat, gave, on being burnt with chromate of lead, the following 

 results : — 



I. 0*2990 grm. gave 0*7575 carbonic acid and 0*1045 water. 



II. 0*3005 grm. of a different preparation gave 0*7620 carbonic 

 acid and 0*1095 water. 



III. 0*2765 grm. of the same preparation as the preceding gave 

 0*7010 carbonic acid and 0*1025 water. 



In 100 parts it contains therefore — 



Carbon 69*09 



Hydrogen 3*88 



Oxygen 27*03 



100*00 100*00 100*00 



