SULPHUROUS ACID ON HYPONITRIC ACID. 69 
window in three different places. In two other operations, 
the tubes burst spontaneously in the place where they were de- 
posited: but there is reason to believe that in these two instances 
the tubes had some defect, or were not hermetically sealed. 
It is thus seen, that under the influence of the strong pressure 
which is necessary to preserve these two bodies in the liquid 
state, time being allowed, they can react on each other, even 
when perfectly dry. What then is formed in the reaction ? 
That the combination is not effected without the previous de- 
composition of one of the bodies, the formation of the green 
liquid (which now presents itself as the subject of examination) 
would seem to indicate. As the collection of this liquid is at- 
tended with some difficulty, it becomes necessary to examine the 
solid product. Great difficulties are also presented here, arising 
from its extraordinary affinity for water ; in consequence of which 
it will be necessary to detail the various successful precautions 
which have been adopted to avoid this source of error. 
In order to obtain a pure, homogeneous, and always identical 
substance, it is necessary to commence by fusing the matter. 
The tube is opened by breaking the point, on which there is an 
immediate explosion; if the proper precautions, however, be 
adopted, it is very feeble. The extremity F is again to be sealed 
with a blowpipe, and the apparatus transferred to an oil-bath, 
the temperature of which is observed by one or two thermome- 
ters. At about 120° cent. (248° Fahr.) the tube is to be re- 
opened. Red vapours escape for a few moments; they need 
not be again intercepted, as the substance does not undergo the 
smallest alteration. Continue to apply heat with care until 
fusion occurs, which commences at 217° cent. (423° Fahr.). The 
upper part of the oil-bath possessing an inferior temperature, 
the whole is not melted till the thermometer attains 230° cent. 
(446° Fahr.). The same points have been repeatedly observed 
by alternately depressing and elevating the temperature. The 
solidification on cooling takes place also about 217° cent. (423° 
Fahr.). This point is more difficult to determine than the fu- 
sing point, because the substance, which is opake when solid, 
becomes transparent in the liquid state, and remains so after 
solidification ; occasionally even until 190° cent. (374° Fahr.). 
If the substance has been previously exposed for some time toa 
moist atmosphere, it melts at an inferior temperature; but this 
property will be again considered. 
