18^3.] M. Ilo$e on Tifaniut^. 369 



vapour actually suspended in the atmosphere at the tune of 

 observation is given in the Edinburgh Encyclopedia, Art. Hygro- 

 metry, attributed to Mr. Anderson.* The hygrometer employed 

 may consist merely of two common thermometers ; one is 

 essentially necessary to the observer for taking the temperature 

 of the air ; and the other is to be compared with it, having its 

 bulb covered with moistened linen ; and will but little increase 

 the apparatus. 



The details are not of difficult investigation; but as fexperience 

 has not yet decided on the propriety of introducing the correc- 

 tion, I shall not at present proceed to any further particulars. 



Article VIII. 

 On Titanium. By M. H. Rose.f 



The oxide of titanium used in these experiments was procured 

 from the rutile of Saint- Yrieix department de la Haute-Vienne. 



When this oxide is fused with carbonate of potash, it forms a 

 compound which sometimes becomes gelatinous when muriatic 

 acid is added ; but it is never as thick as that formed by sihca. 

 Oxide of titanium which has been heated to redness, when 

 moistened and put upon litmus paper, becomes red without 

 affecting the colour of the paper. The effect of this oxide upon 

 litmus is more distinctly shown by putting a small quantity 

 reduced to powder upon a drop of the tincture placed upon a 

 white surface. The oxide becomes red as soon as it is touched 

 by the tincture. 



Oxide of titanium forms compounds with the alkaUes in which 

 it acts as an acid. It is true that it also combines with acids, 

 forming insoluble compounds which do not possess the pro- 

 perties of salts, but rather of double acids. For these reasons, 

 M. Rose considers the oxide of titanium as an acid, and distin- 

 guishes it by the term titanic acid ; but states that, like columbic 

 acid and silica (which is considered as an acid by M. Rose), its 

 affinities at common temperatures are extremely weak, on which 

 account it is difficult to ascertain its properties, and especially 

 to determine its saturating power, and the quantity of oxygen 

 which it contains. 



The author then states that he used three modes to ascertain 

 its saturating power ; first, by examining its combinations with 

 the alkalies ; secondly, those insoluble compounds it forms with 

 some acids ; and lastly, by combining it with sulphur ; and the 



* See also the Edinb. Phil. Journ. No. 4, p. S69. 



f Extracted from the Annales de Chimie et de Physique, t. xxiii. p. 353, 



Neiv Series; vol. vi. 2 i3 



