Professor Apjohn on a new Compound. 165 



IK IK 



3.37 grains gave 0.43 12.75 per cent. 



8.00 „ 1.03 12.87 „ 



9.40 „ 1.13 12.02 „ 



The mean therefore of the numbers in the third column, or 12.55,* is the quan- 

 tity of iodide of potassium as obtained by me in 100 grains of the compound. 



The next step was to investigate the iodine associated, not with the potas- 

 sium, but with the oil, and to effect this the following was the course first 

 pursued. 



A known weight of the compound was decomposed by a slight excess of an 

 alcoholic solution of potash, and the whole was evaporated to dryness, by which 

 the oil was partly volatilized, and partly decomposed. Heat was now cautiously 

 applied, so as to reduce the iodate, which I have already stated to be always 

 formed in such experiment, to the state of iodide of potassium, but not to volati- 

 lize any of the latter salt. The residue, first permitted to cool, was treated with 

 distilled water, and passed through a filter to separate the carbon. The filter 

 was well washed, and the solution, having been reduced to a small bulk by eva- 

 poration, was precipitated by nitrate of silver, and the iodide of silver, first 

 edulcorated three or four times with cold distilled water containing a few drops 

 of ammonia, was finally dried, melted, and weighed. 



In an experiment in which 10.33 grains of the compound were employed, 

 the iodide of silver amounted to 7.41 grains, equivalent to 3.95 of iodine, or 

 38.24 for 100 grains of the compound. Now, if from this we subtract 9-58, 

 the iodine in the 12.55 grains of iodide of potassium, which we have already 

 found to exist in 100 of the compound, we will get for the per centage of 

 iodine, in union with the oil, the number 28.66. 



Fearing that the heat applied in reducing the iodate of potash to iodide of 

 potassium, might have either been insufiiclent for the purpose, or have volatilized 

 some of the latter salt, I recommenced the estimation of the amount of free 

 iodine, or rather of that united to the oil, by a somewhat different process. 



A known weight of the substance was introduced into a test tube with water 

 and zinc filings, and the other end being drawn out at the spirit lamp, it was 



• This contains 9.58 grains of iodine. 



