Experiment has verified this 



598 



introduction of anhydrous baryta, 

 anticipation. 



The upper half of a glass tube 

 filled with, and inverted over, mer- 

 cury, was surrounded by a second 

 glass tube open at both ends and of 

 a diameter about treble that of the 

 former, the annular space between 

 the two being closed at the bottom 

 of the outer tube by a well-fitting 

 cork. The vessel thus formed round 

 the upper part of the inner tube 

 was moreover provided with a small 

 bent copper tube open at the top 

 and closed at the bottom, which 

 was likewise fixed in the cork. The 

 vessel being filled with paraffin and a lamp being applied t6 the copper 

 tube, the upper part of the mercury-tube could be- conveniently 

 kept at a high and constant temperature, whilst the lower end, 

 immersed in the mercury-trough, remained accessible. A glance at 

 the figure explains the disposition of the apparatus. A small quan- 

 tity of the hydrated base was then allowed to rise on the top of the 

 mercury in the tube; and the paraffin bath having been heated to 

 170, the volume of the vapour was observed. Several pellets of 

 anhydrous baryta were then allowed to ascend into the vapour- 

 volume, while the temperature was maintained constant. The mer- 

 cury began immediately to rise, becoming stationary again, when a 

 fraction of the vapour had disappeared, which amounted, the neces- 

 sary corrections being made, to half the original volume. 



XL " Notes of Researches on the Poly- Ammonias." No. X. 

 On Sulphamidobenzamine, a new base ; and some Re- 

 marks upon Ureas and so-called Ureas. By A. W. HOF- 

 MANN, LL.D., F.R.S. Received July 24, 1860. 



Among the numerous compounds capable of the metamorphosis 

 involved in Zinin's beautiful reaction, the nitriles have hitherto 



