404 Dr. Andrews on the Heat developed during the Formation of the 



obtain these compounds in the dry state. At first I attempted to add an excess 

 of bromine or iodine to solutions of known strength of the protocompounds ; but, 

 on endeavouring to expel the excess by heat, I found it difficult, even in the case 

 of the sesquibromide of iron, to avoid the decomposition of the sesquicompound 

 itself, when the solution was concentrated. The object in view was finally 

 effected in a very complete and easy manner, by adding weighed quantities of 

 bromine or iodine to solutions of the protobromide, or protoiodide of iron, con- 

 taining more than twice as much bromine or iodine, as the quantity added. The 

 object of employing a larger proportion of the proto-solutions than the bromine 

 or iodine added would be capable of converting into the state of sesqui-com- 

 pounds, was to prevent the possibility of any free bromine or iodine being pre- 

 sent ; and, as the results were the same, whether the excess of the proto-solution 

 was greater or less, it evidently in no way interfered with the success of the expe- 

 riment. In reducing the results we have, therefore, to remember that the sesqui- 

 compound formed, contains three times the quantity of bromine or iodine added, 

 designated in the tables by Br X 3 and 1x3. 



28. Sesquichloride of iron and iron, Fcj CI3 Aq -|- Fe. 



6r.80 . 



61°.85 . 



63°.34 . 



1°.46 . 



132.8 gm. 



3.0 . 



21.8 . 



0.856 . 



40(3 . 



Mean heat referred to chlorine in CI3 as unit, 402°.5 

 Mean heat referred to iron in Fe^ as unit, 788°. 



29. Sesquibromide of iron and iron, Fcj Br, Aq -\- Fe. 



Th. air 44°.40 . . 46°.70 . . 



T' 44°.46 . . 46°.23 . . 



T^ ..... . 46°.68 . . 49°.02 . . 



Inc. c 2°.23 . . 2°.81 . . 



Th» air. . 

 T. . . 



T^ . . 



Inc. c. 

 Aq. . . 



Sn. (sp. heat 0.73) 

 Vss. . . . 

 Fe^Clj . . 

 Heat of comb. 



47°.20 



45°.77 



50°.84 



5°. 14 



