T04 POISONS : THEIR EFFECTS AND DETECTION. [§§ 75 , 76 . 
water, and fumes when exposed to the air, from becoming saturated 
with aqueous vapour. If exposed to the vapour of ammonia, extremely 
dense clouds arise, due to the formation of the solid ammonium chloride. 
Tiie acid, boiled with a small quantity of manganese binoxide, evolves 
chlorine. Dioxide of lead has a similar action ; the chlorine may be 
detected by its bleaching action on a piece of paper dipped in indigo 
blue ; a little zinc foil immersed in the acid disengages hydrogen. 
These two tests—viz., the production of chlorine by the one, and the 
production of hydrogen by the other—separate and reveal the con¬ 
stituent parts of the acid. Hydrochloric acid, in common with 
chlorides, gives a dense precipitate with silver nitrate. The precipitate 
is insoluble in nitric acid, but soluble in ammonia ; it melts without 
decomposition. Exposed to the light, it becomes of a purple or blackish 
colour. Every 100 parts of silver chloride are equal to 25-43 of 
hydrochloric acid, HC1, and to 63-5 parts of the liquid acid of specific 
gravity 1-20. 
The properties of pure hydrochloric acid gas are as follows :—Specific 
gravity 1-262, consisting of equal volumes of hydrogen and chlorine, 
united without condensation. 100 cubic inches must therefore have a 
weight of 39-36 grains. The gas was liquefied by Faraday by means of 
a pressure of 40 atmospheres at 10° ; it was colourless, and had a smaller 
refractive index than water. 
Water absorbs the gas with avidity, 100 volumes of water absorbing 
48,000 volumes of the gas, and becoming 142 volumes. The solution has 
all the properties of strong hydrochloric acid, specific gravity 1-21. The 
dilute hydrochloric acid of the Pharmacopoeia should have a specific 
gravity of 1-052, and be equivalent to 10-58 per cent, of HC1. 
§ 75. Statistics of Poisoning by Hydrochloric Acid.— The following 
table gives the deaths and sex distribution due to hydrochloric acid for 
five years ending 1916 :— 
DEATHS FROM HYDROCHLORIC ACID IN ENGLAND AND WALES 
DURING THE FIVE YEARS ENDING 1916. 
Accident or Negligence. 
Suicide. 
Males. 34 
Females . . . .15 
Total . 49 
Males.188 
Females . . . .175 
Total . 363 
From 1889 to 1916 there have been two cases of murder from hydro¬ 
chloric acid. The total deaths from hydrochloric acid amount to about 
80 a year. 
§ 76. Fatal Dose. —The dose which destroys life is not known with 
any accuracy. In two cases, adults have been killed by 14 grms. (half 
an ounce) of the commercial acid ; but, on the other hand, recovery is 
