52 ON A GENERAL METHOD OF SUBSTITUTING 



upwards, and by slight tapping a passage opened throughout the w and so 

 of the tube, while the pieces of lead projecting above the surface meltec that 

 application of heat, and by exposing a metallic surface during the time combustion 

 was going on, served to retain all the iodine. 



The results of analysis are as follows : The hydrogen of No. 1 was not weighed, 

 as, from its combustion being effected in the ordinary way without lead, the small 

 end of the chloride of calcium tube was completely covered with small plates of 

 iodine. 



No. 1. 4-893 grains substance burned with chromate of lead, gave 

 4*620 ... carbonic acid. 



No. 2. 7'298 grains substance burned with chromate of lead, litharge, and metallic lead, gave 

 6 '7 59 ••• carbonic acid, and 

 •975 ... water. 



No. 3. 6-85 grains substance heated with carbonate of potash, gave 

 6 707 ... iodide of silver. 



No. 1. No. 2. Calculation. 



Carbon, . . . 25-750 25-25 25-19 C 10 60 



Hydrogen, . . - 1-48 1-26 H 3 3 



Oxygen, ... - - 20-17 6 48 



Iodine, .... 52-909 - 53-38 I 1271 



100-000 100-00 100-00 238-1 



These results correspond exactly with the formula, C 10 H 2 I0 5 + HO. 



Iodopyromeconic acid is monobasic, and forms salts, of which I have minutely 

 examined only those of baryta and lead. It does not appear to form an ammonia 

 salt. 



Todopyromeconate of baryta is readily prepared by mixing together alcoholic 

 solutions of acetate of baryta, and of the acid made slightly alkaline with am- 

 monia. After a short time it deposits a fine network of delicate crystals, of 

 little solubility either in cold or hot water or alcohol. It is alkaline to litmus 

 paper, and at 212° it suffers no loss of weight. 



The following result was obtained on igniting the salt with sulphuric acid : — 



4-49 grains substance gave 

 1-63 ••• sulphate of baryta. 



which corresponds to the formula, Ba O C 10 H 2 I0 5 + HO, as shown by the follow- 

 ing calculation : 





Experiment. 





Calculation. 





Carbon, 



19-068 



C 10 



60 



Hydrogen, 



• .. 



•954 



H 3 



3 



Oxygen, . . 





15-255 



6 



48 



Iodine, 





40-394 



I 



127-10 



Baryta, . . 



. 2384 



24-329 



BaO 



7655 



100-00 100-000 314-65 



