DRINKING WATER FOR TRAVELLERS IN THE TROPICS 507 
Directions for Use. 
(1) Set up the bag, adjust cover and strain in the water to within about four inches of the top, 
using the gauze provided as a strainer.! 
(2) Get a clean stick or something of the kind for stirring the water. Place it down in the 
water and let it stay; do not take it out at any time. 
(3) The treatment of the water consists of adding the contents of tubes of calcium hypochlorite 
(lumpy powder in brown glass tubes), testing the water in an ordnance cup with orthotolidine 
(0.1 per cent solution in ten per cent hydrochloric acid), which is a liquid in vaccine ampoules, 
then when the right colour is obtained, waiting thirty minutes and adding sodium thiosulphate to 
remove the excess of chlorine and destroy its odour and taste. 
(4) The method is as follows; carry out each step carefully :— 
(a) Fill an ordnance cup about half full with water from the bag. (b) Take one of the brown 
glass tubes of calcium hypochlorite, break it while holding it over the cup and dump its contents 
into the cup. Stir the powder into the water with a spoon and pour the water from the cup into 
the bag. (c) Stir the water in the bag thoroughly, then run three cupfuls through one of the faucets 
and pour the water back into the bag. (d) Draw off a cupful of the water through the same faucet. 
Fill the cup to within half an inch of the top. -(e) Break the tip off one of the ampoules of ortho- 
tolidine and shake the fluid into the cup of water. (This is a clear fluid in a tube such as those used 
to contain typhoid vaccine.) Stir this up in the water, using another clean, dry spoon. (f) As 
the water is stirred it begins to turn yellow. This yellow colour tells by its intensity whether or not 
enough tubes of calcium hypochlorite have been added. One may be enough, but it may take two 
or three, or even ten or more. It is necessary to add them one at a time, testing between, until the 
yellow colour deepens quickly to a distinct orange, or orange-red colour. A lemon or canary yellow 
means less than enough, and another tube must be stirred up in a cup of water and added to the 
bag as before. (g) If the colour is lemon yellow, fill another cup half full of water, break another 
tube of calcium hypochlorite into it, stir it up and pour it into the bag. Stir the water in the bag, 
wash out one of the faucets three times, then fill the cup and shake into it the contents of an ampoule 
of orthotolidine. Stir with a clean, dry spoon as before and look for an orange or orange-red colour. 
If the colour is only a lemon yellow, again, at the end of about a minute, put in another tube of 
calcium hypochlorite, and keep doing this until the test no longer shows a lemon yellow, but gives 
an orange or orange-red. (h) When the orange or orange-red colour comes up, enough calcium 
hypochlorite has been added and the water will be ready to drink in thirty minutes. Take the time 
and prepare the solution which removes the excess of chlorine — the chlorine gives the water its 
peculiar odour and taste — from the water. (7) This neutralizing material is sodium thiosulphate, 
and it is supplied as crystals in clear glass sealed tubes. Fill an ordnance cup with water, break 
one tube and shake the crystals into the cup. Stir with a spoon to dissolve and let this cup stand 
until the thirty minutes are up. (7) At the end of about twenty or twenty-five minutes begin 
washing out the faucets. Run five cupfuls of water through each and pour the water back into the 
bag. (k) At the end of thirty minutes pour the dissolved sodium thiosulphate into the bag and stir 
the water thoroughly. (l) The water is now ready for drinking. 
It early became apparent that the calcium hypochlorite was deteriorating 
rapidly, even in the Army ampoules. They generally exploded when opened by 
filing, with the result that much chlorine escaped and more or less of the powder 
was scattered and lost. 
At Monrovia, in Liberia, between July 10 and 30, 1926, we used rain water 
which had been collected from a roof and stored in a cistern. This water was 
clear, but of course not free from impurities. To get a positive test for adequate 
chlorination, it was necessary to add to this water calcium hypochlorite at the 
rate of three or four ampoules to the full bag (80 gallons, or 120 liters). Even 
larger quantities were needed as time passed. 
On July 24, 1926, the other Lyster bag was put to use at a base camp on the 
1 We used Canton flannel instead of gauze. 
