SULPHUROUS ACID ON HYPONITRIC ACID. 71 
is thus introduced, seal the tube by means of a lamp, which 
must be done so expeditiously that nothing can possibly be ab- 
‘sorbed. Another weighing gives the weight of the substance 
introduced. This method of operation must always be adopted 
when a known weight of the material is required. 
The estimation of the sulphur in this compound is made 
without difficulty. Take an excess of diluted ammonia, and drop 
into ita tube containing a known weight of the substance to be 
analysed, the point being broken. The reaction is very violent ; 
coyer the vessel, that portions of the liquid may not be lost by 
the effervescence of the nitric oxide; nothing but this gas then 
escapes. The excess of ammonia is afterwards evolved by boil- 
ing. When the solution is neutral, precipitate, while warm, by 
chloride of barium, being careful to have a very slight excess. 
The precipitated sulphate of barytes contains no sulphite. 
1st. 1°8S81 gramme of substance gave 3°683 grammes of sul- 
phate of barytes, equal to 27°00 sulphur per cent. ' 
2nd. 0°42 gramme gave 0°798 of sulphate of barytes, equal 
to 27°36 per cent. 
Mean of the two experiments gives 27°18 sulphur. 
The nitrogen was estimated by two methods ; by decomposing 
the compound by copper, and by mercury. 
For this purpose the apparatus employed in organic analysis 
was employed, but the oxide of copper was almost entirely re- 
placed by other materials. At the bottom of a long green glass 
tube (sealed at one end), a sufficient quantity of pure carbonate 
of lead is placed; on this a column of recently reduced copper, 
of seven or eight centimetres in length, and then a small tube 
containing a known weight of the substance, which, on being 
opened, is to be filled with copper turnings. The open end is 
directed towards the bottom of the analysing tube ; one or two 
centimetres of oxide of copper and twenty or twenty-two of me- 
tallie copper are next introduced, and the tube closed with a 
good perforated cork, which receives a chloride of calcium tube, 
also connected with a bent tube terminating under an inverted 
jar of mercury. Heat is first applied to the carbonate until 
the gas it evolves is completely absorbed by potash; the copper 
in the anterior part of the tube is then heated strongly, and after- 
wards that in the posterior part ; but the substance to be analysed 
must be protected as much as possible from the action of heat 
until the whole tube has attained a full red heat. When this 
