120 



G. B. TALBOT 



of the laboratory in relation to the source 

 of salt water and upon the type of experi- 

 ments to be conducted. 



One major fault found in some continu- 

 ous-flow systems was that no provision 

 was made to maintain constant pressure 

 when dilferent amounts of water were 

 used. As a result, if small (luantities of 

 water were being used in the laboratory 

 and a large valve was opened at an outside 

 tank, pressure in the system dropped to 

 such an extent that water ceased to flow 

 in the laboratory, and it was necessary to 

 further open the spigots in the laboratory 

 to obtain a flow. Then if a valve at an out- 

 side tank was closed, pressure in the lab- 

 oratory increased sufficiently to disrupt 

 experiments in progress. As a result ex- 

 treme caution had to be observed at all 

 times when valves were opened or closed 

 any place on the system. 



Only two really satisfactory nontoxic 

 materials for handling salt-water were 

 found in use in 1953 — hard rubber and 

 lead. Some experiments were being car- 

 ried out with plastic pipe, however, which 

 gave indications that this material would 

 be superior. Since plastic pipe was much 

 more economical to purchase and install 

 than hard rubber and lead, experiments 



Laboratory Water Tables 



r-r-w—w-r-r-r 



I J "^PiicocH 



-' y 



were carried out at this laboratory with 

 several brands of polyethylene and poly- 

 vinyl-chloride pipe to determine their 

 toxic effects on marine organisms. Some 

 brands appeared to have an initial tox- 

 icity, but after being washed for several 

 hours, none exhibited any toxic properties. 



Several pumps were available which 

 had performed satisfactorily on other salt- 

 water systems examined. These were 

 manufactured specifically for handling 

 brines, acids, alkalis, and other corrosive 

 liquids for industrial applications. Con- 

 struction was of hard rubber or of cast 

 iron lined with nibber so that the liquid 

 being pumped did not come into contact 

 with the metal. 



The salt-water system as constructed at 

 this laboratory is a continuous-flow type 

 (shown schematically in figure 1) which 

 was installed in duplicate so that one unit 

 can be used while the other is being 

 cleaned. The dual system also is used to 

 advantage to provide a standby in case 

 of failure in one system. The pump is 

 a 3-horsepower hard-rubber centrifugal 

 type which furnishes 80 gallons per min- 

 ute at a total head of 30 feet. The same 

 pump is also manufactured in a 1-horse- 

 power model which pumps 40 gallons per 



I 



Outside TonKs 



p a p p 



Ovtrflow Pip* - 



i hp. Hord-rwbbtr 

 Pump — _„ 



Figure 1. — Salt-water system. 



