636 POISONS THEIR EFFECTS AND DETECTION. [§ 8l2. 
Seven persons became affected with lead-poisoning through horse-hair 
coloured with lead. 1 
The manufacture of American overland cloth creates a white-lead dust, 
which has caused serious symptoms among the workmen (Dr G. Johnson ). 
The cleaning of pewter pots, 2 the handling of vulcanised rubber, 3 the 
wrapping up of various foods in tinfoil, 4 and the fingering of lead counters 
covered with brine by fishmongers, have all caused accidents in men. 
The lead in glass, though in the form of an insoluble silicate, is said 
to have been dissolved by vinegar and other acid fluids to a dangerous 
extent. This, however, is hardly well established. 5 
The various glazes used in the pottery manufacture are largely com¬ 
posed of lead compounds litharge, white and red leads being used ; 
some of the glazes are fused with siliceous materials (fritted), but few 
of these silicates are absolutely insoluble in acids \ hence acid vegetable 
juices, especially if heated, are liable to dissolve out the lead from a 
lead-glazed earthenware vessel. Dr Campbell ( Lancet , 1886) has re¬ 
corded a series of cases of poisoning from home-made wine fermented in 
lead-glazed earthenware pans. Thorpe 6 has investigated the composi¬ 
tion of most of the lead silicates used as glazes, and has shown that the 
primary factor governing solubility or otherwise in complex lead silicate 
is the relation between the basic oxides and the acidic oxides. The 
percentage weight of each oxide is divided by its molecular weight ; 
the quotient represents the relative number of that oxide present in a 
definite weight of the silicate—adding all the quotients for the acidic 
oxides gives the total number of acidic molecules, and similarly for 
t . . . No. of acidic molecules 
the basic molecules the ratio = — ———7 -—--—. So long as this 
JNo. 01 basic molecules ® 
ratio is higher than or approximately equal to 2, the solubility of the 
lead Thorpe found to be small, being for the most part below 2 per 
cent. , but when the ratio falls below 2, the quantity of lead dissolved 
(in hydrochloric acid) begins rapidly to increase. 
§ 812. Effects of Lead Compounds on Animals.— Orfila and the 
older school of toxicologists made a number of experiments on the action 
of sugar of lead and other compounds, but they are of little value for 
elucidating the physiological or toxic action of lead, because they were, for 
the most part, made under unnatural conditions, the gullet being ligatured 
to avoid expulsion of the salt by vomiting. Harnack, in order to avoid 
the local and corrosive effects of sugar of lead, used an organic compound, 
a iz. plumbic triethyl acetate, which has no local action. Frogs exhibited 
1 Hitzig, Studien ilber Bleivergiftung. 
Med. Gazette, xlviii. 1047. 3 Journ., 1870, p. 426. 
4 Taylor, Prin. Med. Jurisprud., i. 
5 See Aerztl. Intelligent, f. Baiern, Jahrg. I860 ; Buchner’s Rep. Pharm., xix. 1 ; 
Med. Centrbl., Jahrg. 1869, p. 40. 
6 Journ. Chem. Soc., T., 1901. 
