238 



THE AGIUCULTUEAL NEWS. 



July 24, 1909. 



COPPER AS AN ALGICIDE. 



The group of water plants known as Algae includes 

 the seaweeds and a great variety of fresh-water forms, 

 which occur as scums atid slimes, which give the water 

 peculiar greenish and bluish-green colours, and often 

 imj)art to it an offensive odour and occasionally even 

 render it highly unhealthy. 



Water in the West Indies, in ponds, pools, tanks 

 and reservoirs often supports vigorous growths of algae, 

 and it may be of interest to the readers of the Agri- 

 culfrral N('v:s to know that by the use of copper 

 sulphate such growths may be prevented, or the plants 

 •already developed may be entirely destroyed. 



Bulletin 76 of the Bureau of Plant Industry of the 

 United States Departmi-'nt of Agriculture, entitled 

 Copper as an Ab/irUlr mid DisinfectaiU in. Water 

 l-^upjilics, gives results of a large number of trials, and 

 the amounts of copper sulphate that may be present in 

 the water without in any way injuring it as a drinking 

 water. 



The followinc: statements taken from the conclu- 

 sions and sumnv V of the bulletin already referred to 

 may be of inter. . — 



Experience l.,is demonstrated the practical value of 

 copper .sulphate as an agent for the purification of coulam- 

 inated water, and it is believed that mast of the important 

 conditions likely to obtain have been encountered and success- 

 fully dealt with. Unsuspected features may arise, however, 

 and more complete information on the influence of the 

 chemical constitution and temperature of the water, and on 

 the recurrence of jiollutiiig organisms is very much to be 

 desired. It is therefore urged that water engineers, sanitarv 

 engineers, and others who may be interested keep accurate 

 records of treatments made, and report any unusual cases 

 that may present themselves. 



From the results of over fiftv reservoirs successfully 

 treated for the removal of algae, the following facts have 

 been develojjed : — 



Much less copper is required to eradicate algae fr(:)m 

 reservoirs than would be necessary to destroy algae under 

 laboratory conditions. 



The eftect of this metal upon fish is of considerable 

 im[)ortance and requires more study. 



The ph3-sical and chemical constitution of a water are 

 factors to be considered in determining the quantity of cop- 

 per sulphate to use in a water-supply. 



The elimination of pollutmg fornrs sometimes ir.?kes 

 possible the development of other species, but so far these 

 species have never been the cause of complaint. 



As a result of the sudden destruction of grept numbers 

 of poUuting algae, for a few days innnediately af.ir treatment 

 of a water-supply there is sometimes an increase in odour and 

 taste. 



The use of copper is an efficient emergency method for 

 sterilizing water contaminated with the oacillus of typhoid 

 fever. 



^fetallic copper offers a conven'.jnt and efficient means 

 t)f sterilizing small anounts of water. 



Copper may be useful in the proper disposal of sewage. 



Copper is of great value as a sui^plement to filtration in 

 case of accident or mismanageiuent. 



Under certain conditions copper may be used to great 

 advantage in connexi^ with filtration. 



There is no authentic record of fatal copper poisoning, 

 and many of the best authorities do not consider copper 

 a true poison : they hold that it is a natural constituent of 

 the body and in minute quantities has no effect upon man. 



The suggested medicinal use of copper in cholera, 

 typhoid, and related diseases seems important. 



A very useful, and at the same time, simple 

 method for the application of copper sulphate is as 

 follows : — 



The necessary amount of copper sulphate is put into 

 a bag of coarse mesh and slov.-ly dragged through the water. 

 By a process of gradual solution the water will become 

 impregnated with the -copper sulphate. In large ponds or 

 reservoirs this may be carried out by tying the bag of 

 sulphate behind a boat and quietly rowing about : in smaller 

 ponds or canals the-'i bag fixed to a pole can be dragged 

 through the water by a man walking along the bank. 



The amount of copper sulphate required to completely 

 destroy fresh water algae is very small, but it must be 

 mentioned that more is required in warm countries than in 

 cool. 



When a sufficient amount of copper sul^Jhate was used 

 to give a strength of 1 part in from 4,000,00U to 10,000,000, 

 or say 1 jjound of copper sulphate dissolved in 1,000,000 

 gallons of water, it was found sufficient to destroy nearly all 

 forms of green algae, ;uid in most instan'jjs did not injure the 

 fish in the ponds. 



The proportion in tanks and small receptacles could 

 easily be worked out and experinrin'vS might be tried as to 

 the smallest amount that would T/.irifj' any given body of 

 stagnant water. 



RICE IN BRITISH GUIANA. 



The last report o' Messrs. Sandbach, Parker & Co., 

 of Georgetown, on the rice industry of British Guiana, 

 dated July 9, 19'jC, gives information as follows : — 



The weather has contiiuied very wet during the past 

 fortnight, and very little milling has been done by small mills 

 in the country. The larger factories that have driers installed 

 have been ousy milling for shipment to the West India 

 islands, ind stocks of paddy are getting low. 



Although the area planted this year is somewhat larger 

 than iast, the unfavourable weather experienced during the 

 pf:.st few weeks ha.s_ been responsible for the flooding of 

 several hundred acres, where the returns will at least be poor 

 if any crop is obtained. The planting has been late this year, 

 and the bulk of the October-December crop will not be 

 reaped until late in November. 



Jjocal demand has .somewhat improved, and prices would 

 be better but for the fact that a quantity of inferior rice of 

 various grades is being offered at low rates. 



Shipments to the West India i.slands di'.ring the fort- 

 night amount to 2,800 bags, being principally to Trinidad 

 and Barbados. 



The exports to date are now about the same as they 

 were at this time last year. 



We quote to-day, f.o.b , Demerara, for good export 

 quality : — 



17.«. lOld. to 18s. 'lOld. per bag of 180 ft. gross. 

 \Gs. Ihltoni.ild' „ „ „ 164 1b. „ 



