310 Intelligence and Miscellaneous Articles. 



for obtaining the inorganic matters of plants, yields incorrect results; 

 that the sulphates contained in the plant so treated are in great mea- 

 sure decomposed, and that the sulphuric acid or sulphur escapes in 

 large proportion among the gaseous products of combustion. 



It occurred to M. Caillat to treat the residues of plants, such as 

 lucern, trefoil and sainfoin, with dilute nitric acid, and he succeeded 

 in separating almost the whole of the mineral substances which they 

 contained ; so that the pulpy residue of 10 grammes of the substance 

 employed, after washing and drying, burnt readily, leaving only 18, 

 20, or 22 milligrammes of ashes. This small residue consisted of 

 silica and a little peroxide of iron, substances both insoluble in the 

 acid employed. This method of treating plants always yielded the 

 author a larger proportion of mineral substances than he obtained 

 from the same quantity of the same plants by incineration ; and in 

 certain vegetables he found a much greater quantity of sulphuric 

 acid than has hitherto been stated. 



M. Caillat states, that he found by experiment that the loss of 

 sulphuric acid occasioned by incineration is derived from the decom- 

 position of a part of the sulphate of lime. Thus on intimately mixing 

 with starch and water a known quantity of pure and calcined sul- 

 phate of lime, and incinerating the mass, the collected ashes did not 

 contain as much sulphuric acid as the sulphate of lime employed. 



The author has also stated another direct experiment, which shows 

 that the sulphate of lime converted into sulphuret of calcium by the 

 influence of the organic matter, at a high temperature, is partly con- 

 verted into carbonate of lime by the action of the oxygen of the air. 

 The oxygen gas, burning at once the sulphur of the sulphuret and 

 a portion of carbon interposed, forms sulphurous acid, which is 

 evolved, carbonic acid, part of which remains combined with the 

 lime, facilitating thereby the displacement of the sulphur. — L'ln- 

 stitut, A out 8, 1849. 



BLUE ARSENIATE OF COPPER. BY M. REBOULLEAU. 



The author had proposed to employ the above-named compound 

 both as an oil and as a water colour ; but he has since found that, 

 owing to the action of the oil on the oxide of copper, the colour 

 becomes bluish-green ; in fact, that the arseniate acts with oil like 

 verditer and other blue preparations of copper. 



If equal parts of common arseniate of copper and neutral arseniate 

 of potash be mixed and heated, the compound melts, and yields on 

 cooling a fused, perfectly transparent mass of a bluish-green colour, 

 a vitreous fracture and very fusible. The resulting compound is a 

 double arseniate of potash and copper obtained in the dry way by 

 M. Berthier's process. Whilst the double arseniate is in perfect 

 fusion, if one-fifth of its quantity of powdered nitrate of potash be 

 projected into it, brisk effervescence ensues, and a large quantity of 

 nitric oxide is disengaged. The crucible then removed from the 

 fire contains a magnificent blue substance, formed of sub-arseniate 



