148 On the detection of Arsenical Poisons, $c. [Feb. 



as well as those soluble in that liquid ; but on the occasion of a second 

 death by one of these poisons, which came under investigation before 

 the Police in 1838, I had proof that this opinion was erroneous. 



The deceased was a young female, to whom a large quantity of crys - 

 tallized yellow orpiment (sulphuret of arsenic) had been administered 

 in curry, and in consequence of which she died after a few hours' illness. 

 On examination of the body a quantity of yellow powder was readily 

 separated from the contents of the stomach, and the mucous membrane 

 of that organ was observed to be sprinkled all over with shining gold- 

 like crystals. 



On applying Maksh's process to a portion of the yellow matter, no in- 

 dications whatever of arsenic were obtained. 



A quantity of the powder was then dissolved in liquid ammonia, and 

 Marsh's process applied, still with negative results. 



I then tried the effect of converting the sulphuret into arsenious acid, 

 which was done by boiling the yellow matter with a few drops of 

 nitric acid. On diluting the solution with water, it was found that a 

 single drop tested by Marsh's method gave a most distinct metallic 

 crust, which was readily proved to be arsenic by the application of the 

 silver, copper, and sulphuretted hydrogen gas. 



These facts are of much practical importance, especially in this coun- 

 try, where orpiment is commonly used as a poison. They shew that 

 in all cases where arsenic may have been employed, we must, in the 

 event of Marsh's process proving negative, apply a modification of the 

 experiment I have related, so as to bring the sulphuret of arsenic 

 into the state of an oxide. For this purpose the insoluble parts of the 

 contents of the stomach should be boiled in a capsule of glass or porcelain, 

 with small quantities of nitric acid, until red fumes are no longer given 

 off. The mass should then be diluted with water, neutralized with 

 carbonate of potash or soda, and, lastly, examined by Marsh's method. 



To shew the delicacy of this process, I may state, that I have applied 

 it to the one-tenth part of a grain of orpiment mixed with four ounces 

 of solid and fluid animal matter. By boiling with nitric acid, diluting 

 with water and neutralizing, ten ounces of a liquid mixture were obtain- 

 ed, from half a fluid ounce of which the metal was reduced, although 

 the quantity could not have been quite the 200th part of a grain. 



I have next to notice the only serious fallacy to which this most 

 ingenious method is liable, and which was first pointed out by Mr. 

 Thomson in the Philosophical Magazine for May, 1837. It consists 

 in the indications given by the soluble antimonial compounds, several 

 of which are employed in medicine, one especially as an emetic in the 

 treatment of cases of suspected poisoning. 



