We have been told that the sulphate of copper, when added to any liquid or fluid containing arsenic, will throw down a green precipitate?—Yes, it will have that effect; and I have made that experiment.
Have you made any experiment in order to ascertain whether any green precipitate would be thrown down by sulphate of copper, when applied to any other solution than that of arsenic?—I have tried it with an infusion of onions and animal matter.
(By Mr. Justice Abbott.) What was the result?—A green precipitate resembling that which would have been thrown down, if arsenic had been present.
(Cross-examined by Mr. Sergt. Lens.)
Did you happen to attend when Dr. Edwards was the chemical lecturer at St. Bartholomew’s Hospital, in London?—I was a student in the Borough, at St. Thomas’s and Guy’s.
Then you did not attend yourself, when Dr. Edwards was the chemical lecturer at St. Bartholomew’s?—No, I did not.
Do we understand that you made those experiments previous, or since this circumstance happened?—Both previous to, and since this melancholy circumstance; and particularly that with the nitrate of silver; and I thought it one of the most delicate at the time I made it.
(By Mr. Justice Abbott.) That is the lunar caustic?—Yes, my Lord. When I first made the experiment, about three years ago, I found it the most delicate test of arsenic.
What do you mean by the most delicate test of arsenic?—That is, the smallest portion would be detected by it.
(By Mr. Sergt. Lens.) You found that at first?—Yes, but I have since discovered its fallacy; and it was pointed out by the same means which discovered its delicacy as a test, because it is now ascertained that something else will produce the same appearances.