86 
POPULAR SCIENCE REVIEW. 
by the above-described methods, a sample of very superior black Congou tea 
gave the following results, which he had placed in juxtaposition with the 
numbers obtained after some of the same sample had been infused in the 
usual manner in the teapot (the exhaustion was not carried to excess, no 
second quantity of tea being used), and the leaves re-dried : — 
Original 
Exhausted 
Tea. 
Tea. 
Moisture .... 
. 9-2 
11-1 
Insoluble matter . 
. 58-7 
87-5 
Gum 
. 10*5 
3*8 
Tannin (by gelatin) 
. 15-2 
3-3 
Purification of Drinking-water by simple Chemical Means. — Many of us 
suppose that the best method of dealing with water not sufficiently pure for 
drinking is to pass it through one of the Silicated Carbon Company’s filters, 
or one of Spencer’s magnetic carbide filters. It would seem, however, from 
Mr. Crookes’ advice to the medical staff that is gone to the West of Africa 
(published in the “ Chemical News,” November 14), that a simpler and 
better means of dealing with extremely foul water is to be found in the 
ABC process. Under the name of A B C compound a mixture of sulphate 
of alumina, clay, and charcoal has been successfully used by the Native 
Guano Company for the purification of sewage. At their works he has 
repeatedly seen the sewage of such places as London, Paris, Hastings, and 
Leeds, converted in the course of a quarter of an hour, from an offensive- 
looking, vile-smelling liquid, into water, bright, clear, inodorous, and taste- 
less, non-putrescible, and so free from injurious matter as to allow delicate 
fish to live and thrive in it. With a little necessary modification he con- 
siders that a mixture capable of acting thus on town sewage is the most 
suitable for the purification of water for drinking purposes on the Gold 
Coast. He would suggest that the charcoal be omitted, and its place sup- 
plied by a permanganate. The ordinary potash salt will do, but if pro- 
curable in time he has reasons for believing that permanganate of lime 
would answer the purpose better. He has prepared a mixture of — 
1 part of permanganate of lime, 
10 parts sulphate of alumina, 
30 parts fine clay, 
and finds that when he adds this to London sewage, in the proportion of 
20 to 10,000, the purification is very satisfactory, and the settlement rapid. 
With foul ditch water a less quantity will do. The mixture can be filtered, 
instantly yielding a bright filtrate, or it can be allowed to settle for a 
quarter of an hour, when the supernatant water can be poured off equally 
bright. He is not prepared to say what the price of this mixture would 
be, but it would probably not be many pence per hundred gallons of water. 
We think this recommendation extremely valuable. 
Preparation of Rabbit's Hair for Felt Hats. — In No. 40 of “ Hermanns 
Farber Zeitung,” it is said that rabbit’s hairs were formerly treated with a 
solution of mercury in nitric acid, for the purpose of enhancing their felt- 
ing properties. A mixture of nitric acid and treacle is proposed as a substi- 
tute. 
