1835.] Scientific Intelligence. 73 



growth, provided that the ground be not too dry, nor hard, nor 

 marshy. 



2. That the sides of the hills are better suited for it than the 

 summits, and if the summits are marshy, the inferior parts of the 

 mountains will be proper for it. 



3. It is remarked on the Alps, that the larch succeeds better in a 

 northern than in a southern exposure. The difference is sometimes 

 so striking, that in vallies running from east to west, it is not un- 

 common to see the side exposed to the north covered with larches, 

 and that exposed to the south, with scarce a tree. This may be 

 ascribed to the irregularity of the spring, but will not apply to this 

 country. 



4. The plantations of larch in this country are too thick, the 

 trees being generally planted at a distance of 3 or 4 feet. De CandoUe 

 considers that the young trees ought to be planted at a distance of 

 10 feet, and if planted closer, they should be gradually thinned for 

 20 years. 



He recommends likewise, that for security, new seed should be 

 brought from the Valais, where the cones are dried by the heat of 

 the sun, and not from the Tyrol, where fire is employed for this 

 purpose. 



M. Em Thomas sells them at the rate of 2i francs (2s. Id.) the 

 half Kilogramme (1 3 lb. troy). M. Thomas advises that the trees 

 should be always transplanted in autumn and not in spring. 



III. — Arsenic in English Sulphuric Acid. 



VoGEL of Miinchen, infers from his experiments on sulphuric acid. 



1 . That the IS^ordhausen acid, prepared from the sulphate of iron 

 contains no arsenic ; the precipitate with sulphuretted hydrogen being 

 pure sulphur. 



2. Concentrated English sulphuric acid prepared in leaden cham- 

 bers contains arsenic, and the precipitate produced in it by a current 

 of sulphuretted hydrogen, consists of sulphur and orpiment. 



3. No precipitate of sulphur takes place, in consequence of a 

 current of sulphuretted hydrogen being passed through English 

 sulphuric acid, diluted with from four to six parts of water ; the 

 precipitate consisting of an orange yellow powder or orpiment. 



4. Rectified English sulphuric acid contains no arsenic ; this sub- 

 stance remaining in the residue. The rectified acid diluted with water 

 is not rendered muddy by sulphuretted hydrogen. The German 

 sulphuric acid diluted with water, becomes white when the latter gas 

 is passed through it, as it always contains sulphurous acid. 



5. The arsenic always exists in sulphuric in the form of arsenious 

 acid, never as arsenic acid. 



6. Concentrated boiling sulphuric acid can dissolve one»third of its 

 weight of arsenious acid, of which the greater part separates on 

 cooling. The arsenious acid may be precipitated in a great measure 

 from the concentrated sulphuric acid when cooled, by absolute 

 alcohol, although it is somewhat soluble in alcohol. 



