Chemical Science. 17S 



it became yellow, and white on cooling, but did not absorb much 

 oxygen, only from 3 to 5 per cent. Heated very powerfully with 

 oil, no change was produced. M. Peschier thinks that, perhaps, 

 this powder is the radical of titanium, and may be analogous to 

 borax. It gave the odour of phosphorus when moistened with mu- 

 riatic acid. He concludes, also, from the examination of a small 

 specimen, that the crystals of titanium, described by Dr. Wollaston, 

 are a titanite of iron, analogous to the mamillated substance ob- 

 tained by Laugier. There are, probably, not many persons who 

 will join in this opinion, without some further and powerful reasons. 

 M. Peschier states that he has never been able to ascertain any 

 action of the ferro-prussiate of potash on salts of titanium, and that 

 it affords a certain means of separating iron from them : also that 

 after the iron is separated, the infusion of galls is the only re-agent 

 which will completely separate the titanium. For this purpose, care 

 must be taken to evaporate the liquids submitted to its action, to 

 dryness, to heat the produce to bright redness, to wash with 

 water, and separate the insoluble portion, to destroy the carbona- 

 ceous part; wash again, and heat to redness again, and so on, two 

 or three times. — Bib. Univ. xxvi. 43. 



9. TurrtU's Menstruum for etching Steel Plates. — Take four parts, 

 by measure, of the strongest pyrolygneous acid, chemically called 

 acetic acid, and one part of alcohol, or highly-rectified spirits of 

 wine ; mix these together, and agitate them gently for about half 

 a minute ; then add one part of pure nitric acid ; and when the 

 whole are thoroughly mixed, it is fit to be poured upon the steel 

 plate. 



When the mixture is compounded in this proportion, very light 

 tints will be sufficiently corroded in about one minute, or one 

 minute and a half; and a considerable degree of colour will be 

 produced in about a quarter of an hour ; but the effect may be 

 produced much quicker, by the addition of more nitric acid, or it 

 may be made to proceed slower, by omitting any convenient por- 

 tion thereof. 



When the mixture is poured off the plate, it should be instantly 

 washed with a compound made by adding one part of alcohol to 

 four of water, and the stopping varnish laid upon any part that is 

 sufficiently corroded, bhould be thoroughly dry before the biting is 

 repeated. Care should be taken to keep the mixture out of reach 

 of the sun or any artificial heat, because its valuable properties, 

 for this purpose, would thereby be changed. It will be necessary, 

 alr.o, to observe that no more of the ingredients should be mixed 

 than are wanted for present use, as the mixture will be greatly 

 changed if kept many hours. 



The stopping varnish that answers the purpose best, is made by 

 dissolving the best Egyptian asphaltum in the essential oil of tur- 

 pentine, which dries sufficiently quick for all desirable purposes. 



