PHAEMACOLOGY OF THALLIUM 
3 
Lamy obtained thallium by neutralizing the slime in the lead 
chamber of a sulphuric-acid plant with lead oxide or calcium oxide 
and extracting with hot water. The solution was concentrated, and 
thallous chloride was precipitated by the addition of hydrochloric 
acid. After washing with dilute hydrochloric acid, the product 
was decomposed with sulphuric acid, and impurities were removed 
by hydrogen sulphide. The filtrate was concentrated and metallic 
thallium precipitated by zinc or by electrolysis. Thallium has 
also been obtained by extraction by sodium carbonate, precipita- 
tion of thallous sulphide in the presence of potassium cyanide, 
oxidation to sulphate, and precipitation with zinc. The precipitated 
metal is fused in a stream of hydrogen or in the presence of oxalic 
acid to prevent oxidation. A number of various modifications of 
these methods have been suggested {66^ (S4, 87, 107). 
Thallium is a soft, white metal with a grayish tinge, resembling 
tin in appearance. When exposed to the air, a dark-gray film of 
oxide rapidly forms, which is soluble in water. On paper the metal 
makes a mark resembling that produced by metallic lead. It has a 
specific gravity of 11.8, is somewhat softer than metallic lead, and is 
very malleable. Its chemical symbol is Tl, and its atomic weight 204. 
Thallium forms two series of salts — thallous compounds, in which 
the metal is monovalent, and thallic compounds, in which it is 
trivalent. By treating the metal, the oxide, or the hydroxide with 
the proper acid, a series of salts is obtained. These are usually 
white crystalline products, soluble in water. 
Thallic salts are reduced to thallous salts on boiling, which pro- 
cess precipitates insoluble thallic hydroxide. Microscopically, 
0.0016 milligram of thallium has been detected by precipitation of 
thallous chloride and 0.003 milligram by precipitation by yellow 
thallous iodide. Thallous sulphide (TI2S) is incompletely precipi- 
tated by hydrogen sulphide in the presence of mineral acids and 
completely precipitated in the presence of acetic acid. The sulphide 
is not soluble in ammonium sulphide {107^ 108, 122). The existence 
of a number of sulphates has been claimed {107^ 108). Pale-yellow 
thallous chloroplatinate is precipitated on the addition of 
hvdrochloroplatinic acid, and it is claimed that this reaction will 
detect 0.000,008 milligram of thallium. 
Thallium has been employed in the manufacture of optical glass 
and in the electric-lamp industry. The acetate, the sulphate, and 
the nitrate have been used in medicine. 
DETERMINATION 
Thallium may be qualitatively determined by the characteristic 
green line in the spectrum (55, 100., 107), as well as bv chemical 
methods {133). The detection of 0.000,008 milligram of thallium 
by precipitation with chloroplatinic acid has been reported. Olmer 
and Tian {llJf) claim that the limit of detection with a spectroscope 
is 1: 500,000,000 (0.002 milligram per liter, or 2 parts per billion). 
In a Marsh apparatus, a stain is produced somewhat similar to an 
arsenic stain; however, the thallium stain produces a yellow color 
with iodine and is insoluble in ammonium sulphide. 
