290 
ON THE DETECTION OF ARSENIC. 
the flame as it burns has a different appearance; the flame is 
yellowish, transparent and deposits only water. 
Should you wish to obtain the arsenic in the form of arse- 
nious'acid, then take a glass tube from ^ to \ an inch in diame- 
ter, or according to the size of the jet of flame, and eight or ten 
inches in length, and hold it vertically over the burning jet of 
gas in such a manner that the gas may undergo perfect com- 
bustion, and the arsenic combined with it becomes sufficiently 
oxidized; the tube will thus, with proper care, become lined 
with arsenious acid, in proportion to the quantity originally 
contained in the mixture. 
When the glass tube is held at an angle of about 45 degrees 
over the jet of flame, three very good indications of the pre- 
sence of arsenic may he obtained at one operation, viz.: me- 
tallic arsenic will be found deposited in the tube at the part 
nearest where the flame impinges, arsenious acid or white ar- 
senic at a short distance from it, and the garlic smell can be 
readily detected at either end of the tube. (Marsh.) 
These indications of arsenic are manifested as long as the 
process is continued, or the supply of gas kept up. 
It is asserted that T oJoo of arsenious acid in solution is 
manifested in a short time by this process. 
Marsh says, that with his apparatus he has obtained distinct 
metallic crusts when operating on as small a quantity as one 
drop of Fowler's solution, which contains only T |- -th, of a 
grain. The presence of arsenic in artificial orpiment and re- 
algar, in Scheele's green, and in the sulphuret of antimony, 
may be readily shown by this process when not more than § 
grain of these compounds is employed. 
In cases where the above described apparatus cannot be 
easily procured, its place may be supplied by simpler means. 
Take a wide mouth vial, fitted with a perforated cork, through 
which a tube drawn at one end to a fine point passes. (See 
fig. 5th.) 
By putting the liquid you wish to examine, into this vial 
together with zinc and sulphuric acid, and covering the 
whole with a layer of sweet oil, about two lines in thickness, to. 
