402 Mr. Richardson on the Composition of Coal. 



contained in the Coal. Treated with muriatic acid, they afforded not the 

 slightest perceptible trace of carbonic acid. When boiled with carbonate 

 of soda, the clear filtered solution, saturated by nitric acid, produced not 

 the smallest appearance of a precipitate with a salt of barytes. 



The estimation of the carbon and hydrogen was partially made by means 

 of oxide of copper, but generally with melted chromate of lead. The ap- 

 paratus was • perfectly the same as that employed by Professor Liebig, the 

 only difference being in the use of the above salt, because the quantity of 

 oxygen given off ensured a more perfect oxidation of the carbon and hy- 

 drogen. A more exact account of the employment of this substance will 

 be found in another memoir. 



With respect to the method employed in the determination of the azote, 

 it will be necessary to enter more minutely into particulars (though perhaps 

 a digression from the proper subject of this memoir), to show that no ex- 

 ertion on my part has been wanting to obtain an exact result. Five or six 

 analyses were made with the apparatus which Professor Liebeg has already 

 described for the absolute estimation of azote. The azote in all these 

 analyses amounted to nearly 4 per cent. When it is remembered how 

 small the quantity of sal ammoniac is, which is obtained in every gas ma- 

 nufactory, this amount will at once appear much too great. 



The method of determinng the azote by means of its relation to the 

 carbonic acid was then resorted to, but it was found impossible to measure 

 the volume of the azote. We could only in this way guess at the true 

 quantity of azote, and it appeared to be as 1 h. : 100 co 2 . 



At the suggestion of Professor Liebig, the following plan was then pur- 

 sued. The apparatus, a diagram of which is given in the opposite page, 

 consisted of an ordinary tube of combustion a, about 50 centimetres long, 

 connected with a tube b, that was again in union with a tube c, which pass- 

 ed into a receiver d, partially filled with mercury. A part of the tube c 

 remained always above the level of the mercury in the receiver d. The 

 tube of combustion a contained in the end about two inches of hydrate of 

 lime, then an inch pure oxide of copper, afterwards the mixture of the 

 substance with oxide of copper, washings of the same, and oxide of copper 

 made in the usual way, and lastly copper. The tube b was filled with hy- 

 drate of potash. The whole apparatus being arranged, the receiver d was 



