180 M. C. Lea on Picrie Acid. 
carefully performed with Liebig’s proportions, the lixiviate al- 
ways contains undecomposed cyanid of potassium, it occurred to 
me to try the effect of a more thorough oxydation, and the result 
proved very favorable. The following was the course adopted. 
Of roasted ferrocyanid of potassium 850 grammes are mixed 
with 818 grammes of thoroughly dried carbonate of potash in 
grains, and fused in an iron vessel. When decomposition is 
complete, the vessel is a little cooled and 1900 grammes of re 
lead are to be added, not all at once, but 300 to 400 grammes 
at a time, with intervals of 10 minutes, stirring and keeping up 
heat enough to retain the whole in a state of fusion. 
After the last addition of red lead the mixture is suffered to 
remain half an hour on the fire to complete the reaction. Heat 
is applied in all for about four hours. In this way the eyanid 
of potassium becomes thoroughly oxydized. The process 18 
concluded in the usual manner, and 500 grammes of urea are 
obtained. No particular precaution is necessary during the 
usion, er even the lixiviation with cold water, but in evapo- 
rating the solutions the greatest care must be taken to carry 
off the vapors.* 
Philadelphia, April, 1861. 
Art. XX.—Contributions to the History of Picric Acid; by 
M. Carey Ln, Philadelphia. 
Solubility in Sulphuric Acid. 
If cold saturated aqueous solution of picric acid be mixed with 
sulphuric acid diluted with an equal volume of water, the fol- 
lowing results are obtained: 
1 vol. solution of picrate, 4 vols. dilute ) No precipitate, solution remain- 
sulphuric acid. (1 vol. acid, 2 vols. water.) {_ ing as colorless as water. 
* For continuation of Mr. Lea’s “Contributions,” see p. 210. 
