1835.] Scientific Intelligence. 473 



As the permanency of the benefit resulting from the application of 

 corrosive sublimate to prevent dry rot from affecting the timber of ships 

 is matter of pure experiment, it would only be speculating to give any 

 opinion at the present time upon the subject. But as far as the expe- 

 riments have gone I have reason to know that the results have been 

 highly satisfactory, not only with regard to the preservation of the 

 timber, but also in reference to the health of the seamen, upon whom 

 it was supposed by some, on what grounds it is not easy to discover, 

 that the mercurial salt would produce deleterious effects ; neither is 

 there any reason for anticipating the detriment, which the queries of 

 my correspondent suggest, to the copper sheathing from the same 

 influence. — Edit. 



VIII. — Mode of preserving Iron and Steel from rusting. 



Several methods of preventing instruments of steel and iron from 

 oxidating are well known, such as covering them with mercurial 

 ointment, grease, oil or marrow, or placing them in calcined lime. 

 The former of these I have found the most effectual as well as the 

 most convenient mode. 



M. Payen has, however, lately proposed a new plan for accom- 

 plishing the same object. He found that a saturated solution of car- 

 bonate of soda mixed with its own volume of water, disengaged only 

 ToW P arfc °f its volume of air, and preserved iron from rusting, and 

 did not lose this power even when diluted with twenty-five times its 

 volume of water. A saturated solution of borate of soda, as well as 

 a mixture of water and ammonia, disengaged no gas nor underwent 

 any contraction, but preserved iron from oxidating. Saturated lime 

 water diluted with an equal volume of water possessed the same 

 power. A saturated solution of potash diluted with 1000 and 2000 

 parts of water, preserved iron, but when saturated with a current of 

 carbonic acid, the oxidation of the metal occurred as in common water. 

 A saturated solution of potash diluted with 4000 or 3000 parts of 

 water, had not the property of preventing oxidation, and upon turn- 

 sol this solution exhibited an alkaline re-action. 



M. Payen, sensible of the impracticability of immersing surgical 

 instruments in a liquid, suggests the propriety of forming a varnish 

 the saturated solution of potash, and gum tragacanth. 



He made a comparative experiment upon muskets, one of which 

 he varnished over, and the other was left in its natural state. After 

 a lapse of fifteen days the former was quite bright, while the latter 

 was rusted. He considers thatthe solutions of soda will be preferable 

 to those of potash, because they are less deliquescent. The effects 

 of these solutions in preventing oxidation were so decided, that he 

 compared carefully the consequences when iron was placed in common 

 water. About 20 minutes after immersion a thin opaline halo sur- 

 rounds it, which increases in size and intensity. At the end of an 

 hour it is sensibly brown, and gradually a deposit begins to form on 

 the greatest part of the iron, and at the bottom of the vessel. 



