172 Mr. E. W. Davy on the compai-ative Value of Peat 



baryta necessary to precipitate the sulphuric acid present, was 

 added to each. 



After recording the above observations, a further addition of 

 BaCl was made to each of the solutions in the first fifteen experi- 

 ments, and the results noted down after a lapse of fourteen hours. 



In Exps. 1 and 2 the quantity of BaO NO^ was increased. In 

 Exp. 3 a precipitate of BaO NO^ was produced. On the appli- 

 cation of heat to these solutions the precipitates dissolved, show- 

 ing that no BaO SO^ had been deposited. 



In Exps. 4, 5, and 6, there was a turbidity occasioned by 

 BaO S03. 



In Exps. 7, 8, 9, 10, 11, 12, 13, 14, and 15, there was a pre- 

 cipitate of BaO S03. 



The addition of a large quantity of BaCl to Exp. 19 caused a 

 copious precipitate of BaO SO"*. 



From these experiments, it will be seen that the amount of 

 BaO SO^ precipitated is influenced by the quantity of BaCl 

 present in the solution. We have not ascertained whether the 

 presence of other salts would have produced the same eflfect. 



In the experiments where nitrate of baryta alone is preci- 

 pitated, a confirmation of Berthollet's law of chemical affinity is 

 afforded. 



Sulphate of baryta we find to be also soluble in dilute hydro- 

 chloric acid and aqua regia, but not to the same extent as in 

 nitric acid. In the estimation of sulphur in substances where it 

 exists in small quantity, such as in vegetable and animal sub- 

 stances and in metals, and where, owing to the necessity of ope- 

 rating upon a large amount of material, and consequently of 

 taking a proportionate quantity of nitric acid, we have no doubt 

 that errors similar to tliose which we experienced have frequently 

 occurred. 



XXII. On some Experiments made with a view to determine the 

 comparative Value of Peat and Peat-charcoal for Ap-icultural 

 purposes. By Edmund AV. Davy, A.B., M.B., M.R.I.A., 



Lecturer on Chemistry in the Carmichael School of Medicine, 

 ^c, Dublin*. 



AT no former period has the importance of animal excremen- 

 titious matter to agriculture been so clearly understood as 

 at present; while the growing attention which is now paid to 

 the sanitary condition of towns, and the methods which have 

 been discovered of deodorizing such matter, aflford increased faci- 

 lities of converting it into the most valuable manure. 



Many substances, as chlorine, the chloride of lime and of zinc, 

 * Communicated by the Author. 



