2 so Dr. Thomson on some of the compounds of chromium . 
APPENDIX. 
Since the preceding paper was drawn up, I have found that 
when green oxide of chromium is precipitated by a fixed 
alkaline carbonate, we cannot free it from the fixed alkali by 
washing. This probably occasioned the want of success 
which attended some of the experiments related in the second 
section of the paper. 
