Sir H. Ddvy on Preserving the Copper Sheathing of Ships. 203 



lutions, evaporations, and exposures to a very strong heat, are 

 necessary to effect this purpose completely. 



Such is the series of minute operations which I found it 

 indispensable to follow in the analysis of minerals with a base 

 of titanium (of which the number is much greater than is 

 commonly supposed), and by the aid of which the black fo- 

 liated mica of Siberia — which, according to Klaproth, is com- 

 posed of silica 42-50, alumina \\'50, magnesia 9, oxide of 

 iron 22, manganese 2, potash 10, loss by ignition 1 ; total 98 

 — has furnished me silica 24, alumina 8*50, magnesia 5, per- 

 oxide of iron 30, manganese 0'70, titaniiun 21, potash 5*70, 

 loss by ignition 2'75 ; total 97"65. The talcs, the chlorites, 

 and the steatites gave me, by following the same process, 

 from 0-19 to 0-30 of a substance which, like that I have 

 designated by the name of titanium in mica, forms also, like 

 the titanium extracted from rutile, a gelatinous mass, trans- 

 parent and yellowish, by the evaporation at a moderate heat 

 of its solution in the hydrochloric acid ; furnishes like that, by 

 the saturation of its solution in an acid, a white, gelatinous and 

 very bulky precipitate ; by the infusion of galls a yellowish 

 precipitate, which augments by a slight supersaturation of the 

 acid ; becomes brown, and is in great measure dissolved by 

 the addition of the re-agent, giving to the liquid the colour of 

 blood; is soluble in the pure alkalies; forms double salts 

 with all the acids ; becomes insoluble in acids by the effect of 

 a strong heat, and consequently possesses all the characters 

 of titanium, with the difference only that with the infusion of 

 galls it does not furnish an abundant orange-red precipitate, 

 and does not always take a lemon-coloured tint by heat : but 

 these anomalies, which appear to me of little importance, may 

 be classed with many others which this substance presents. 



Such are the reasons which have induced me to communi- 

 cate this process. But as I am fully sensible of the force of an 

 opinion given by a philosopher of M. Vauquelin's merit, I 

 submit it to the experience of chemists more used to this 

 species of research than I am, and shall gratefully receive any 

 information on the subject that may be transmitted to me. 



XXXIV. Additional Experiments and Observations on the Ap- 

 plication of Electrical Combinations to the Preservation of 

 the Copper Sheathing of Ships, and to other Purposes. By 

 Sir Humphry Daw, 'liarf. P. U.S.* 



¥ HAVE already had the honour of cojnmunicating to the 

 -* Royal Society tlic results of my first researches on the 



- IVoin the Pliil. Trans, for 1R24, Part II. Read June 17, 18:34. 



( ' c 2 modes 



