1826.] Sulpho-Naphthalic Acid. 195 



imperfections, arising principally from the presence and action 

 of so much carbonaceous matter. The following was ultimately 

 adopted. 



A quantity of peroxide of copper was prepared by heating 

 copper plates in air and scaling them. A sufficient quantity 

 of pure muriatic and nitric acids were provided, and also a 

 specimen of pure native carbonate of baryta. Seven grains of 

 the salt to be examined were then mixed with seven grains of 

 the pulverized carbonate of baryta, and afterwards with 312 

 grains of the oxide of copper. The mixture being put into a 

 glass tube was successively heated throughout its mass, the 

 gas liberated being passed through a mixture of baryta water 

 and solution of muriate of baryta. It was found that no sul- 

 phurous or sulphuric acids came off, or indeed sulphur in any 

 state. The contents of the tube were then dissolved in an ex- 

 cess of nitric and muriatic acids, above that required to take up 

 all that was soluble ; and a little solution of muriate of baryta 

 was added for the sake of greater certainty. A portion of sul- 

 phate of baryta remained undissolved, equivalent to the sul- 

 phuric acid of the salt experimented upon, with that contained 

 accidentally in the oxide of copper acids, &c. This sulphate 

 was collected, washed, dried and weighed. Similar quantities 

 of the carbonate of baryta and oxide of copper were then dis- 

 solved in as much of the nitric and muriatic acids as was used 

 in the former experiment ; and the washings and other opera- 

 tions being repeated exactly in the same way, the quantity of 

 sulphate of baryta occasioned by the presence of sulphuric acid 

 in the oxide, acids, c. was determined. This, deducted from 

 the weight afforded in the first experiments, gave the quantity 

 produced from the sulphuric acid actually existing in the salt. 

 Experiments so conducted gave very uniform results. The 

 mean of many indicated 8*9 grains of sulphate of baryta for 10 

 grains of salt used, or 89 grains per cent., equivalent to 30*17 of 

 sulphuric acid for every 100 of salt decomposed. 



In the analytical experiments relative to the quantity of car- 

 bon and hydrogen contained in the salt, a given weight of the 

 substance being mixed with peroxide of copper, was heated 

 in a green glass tube. The apparatus used consisted of Mr. 

 Cooper's lamp furnace, with Dr. Prout's mercurial trough ; and 

 all the precautions that could be taken, and which are now 



