174 



or mercuric chloride,' gives a solution which is stable for a long time at room tempera- 

 ture, but which decomposes on heating, gi\'ing a precipitate of the metallic sulfide 

 and some free sulfur. Solutions of this type can also be made alkaline without the 

 formation of any precipitate. They then fall in the second class above. 



The reducing power- of the wood is due to the carbonyl groups in the cellulose 

 molecule, and is active only in alkaline solutions. Since most metals precipitate in 

 ordinarv alkaline solutions, special solutions must be used such as the thif)sulfate 

 solution above. 



The timber is impregnated with the alkaline solution and subsequently heated, 

 whereupon the reducing action of the wood causes precipitation of a metallic oxide 

 or the free metal. The heating merely serves to speed up the reaction. 



Treatments Nos. IB and 2, above, depend entirely on the reducing power of 

 the wood. In No. 3, the decomposition depends on heat alone. Treatment No. 5 

 gives a decomposition which is a mixture of the two types. 



Four sets of test pieces with the above treatments were placed at various stations 

 in the bay. All showed some retardent action against borers, as compared with im- 

 treated wood, but within one season all were attacked to some extent. Some of the 

 treatments devised may have value for other purposes, but apparently none of the 

 inorganic treatments which we have studied have any permanent value in the pro- 

 tection of marine piling against borer attack. This conclusion is strengthened by 

 the rapid failure in marine use of proprietary- metallic salt preparations, such as 

 colloidal metallic selenium and tellurium in the Protections tests of this Committee, 

 and of mercuric chloride and oleate as tested in the East. 



EFFECTS OF CHLORINE ON TEREDOS 



The following experiments were carried out at the request of the National Re- 

 search Council for the purpose of determining the effects of chlorine liberated in 

 sea water upon adult teredos in their burrows, for which, as a means of practical 

 control, apparently extravagant claims have been made upon this coast. 



Three pieces of 2" x 4" timber infested by Teredo navalis were obtained from 

 Dumbarton through the Committee biologist. One was used as a control, and was 

 kept in fresh bay water throughout the test. The other two were exposed to various 

 concentrations of chlorine in bay water. 



The experiments extended over a period of several weeks, during which time the 

 teredos were alternately exposed to chlorine and fresh ba\' water. The time of expo- 

 sure to chlorine varied from 24 to 72 hours. After being exposed to chlorine, the borers 

 were usually left for about 24 hours in fresh bay water, but in all cases observed, 

 the activity of their siphons indicated complete recovery in a much shorter time 

 than this. 



The concentrations of chlorine possible when the gas is liberated in sea water 

 under no pressure other than atmospheric, are necessarily very small. The initial 

 concentrations of chlorine used in our experiments were from 30 to 120 parts per 

 million parts of sea water. These concentrations dropped off rapidly since the con- 

 tainers were not gas-tight. In practically all cases, however, there was sufficient 

 chlorine to give a distinct odor during most of the time of exposure. 



'In the case of the mercuric chloride, the stability of the solution is somewhat increased by the 

 addition of a little Nai.CO, or NaOH. 



-An actual determination of the reducing power of Douglas fir sapwood on Fehling's solution, gave 

 a value of O.U pounds of CuSOj reduced to Cu.O per pound of wood. The determination was made on 

 sawdust which had been extracted with benzene and alcohol to remove all except the structural material 

 of the wood. 



