maintain a given pH range. Camples held near a pH of 7 produced m^arly 

 pure >'-monohydrate , while those restricted to a pH of h.$ or less produced 

 mainly thoTC-form (see X-ray diffraction patterns b and c in Figure l). 

 Further work is contemplated along these lines so as to permit more exact 

 delineation of the conditions for the formation of these oxides. 



Wood blocks have been treated variously by vacuum-pressure and steeping 

 methods using ferrous sulfate in the first treatment and ammonia, ammonium 

 hydroxide, or pyridine in the second. It is not possible to determine 

 what specific forms are actually obtained in these treatments, but it is 

 reasonable to assume that they will consist of the oxides of a definite 

 group, nansly, magnetite and;/- and/'-monohydrates. • It is hoped that the 

 use of different methods will afiect the final product and thereby obtain 

 differences vfhich may affect their performance. The physical state of 

 the oxides should be eventually like that of rust from metallic iron, 

 since these forms are considered to be either intermediate in the oxidation 

 of iron or the same as the ultimate product. 



HEAVY M.TiVL SULFIDES 



Compounds of the heavy metals are well established as being toxic to animal 

 life and are known to produce important physiological effects in trace 

 amounts. Copper sulfate, for example, is -.ridely used as an economic poison 

 in the control of a large nimiber of species in the general biological groups, 

 m^ollusks and arthropods, to which the various species of marine borers be- 

 loniT-. This compound is an effective molluscacide in very low concentra- 

 tions, and is currently in large scale use for this piirpose (12), in canals 

 and similar constricted bodies of water. But this particular compound 

 would not be suitable for the preservation of marine timbers because it 

 would be rapidly lost through the serious leaching action of the sea, Ihe 

 sulfides of copper and other like metals are, however, extremely insoluble 

 and, therefore, it is conceivable that they may be useful in -this capacity. 

 The sulfides included in the present test program are those of copper, 

 lead, mercury, nickel, zinc, cadmium, iron and silver. 



The particle size of copper sulfide varies with different methods of pre- 

 cipitation. Observations as to the nature of the suspensions and micro- 

 scopic examinations of the po^vders show that the following methods produce 

 particles of decreasing size in the order listed. 



(1) Heat treatment of equal parts of S,'> copper sulfate and 12^ 

 sodium thiosulfate. 



(2) 2.5a; copper sulfate, plus hydrogen sulfide, 



(3) Equal parts of 2,5;" copper sulfate and 2,S% ammonium sulfide. 



When blocks ..'ere impregnated v^ith solutions of method (1) above and heat 

 treated, the procedure used by Ramage and Burd (13), the wood became a 

 greenish-gray in color, but judging by the color the actual amount of 



K - 6 



