Progress of Foreign Science. 149 



bat he considers the black flocks, which are obtained on 

 washing the residuum of the calcination of that salt in an 

 earthen retort, as not being a quadri-carburet of iron, but a 

 mere mixture of the two ingredients. Pure silica ignited ia 

 an earthen retort with anhydrous ferro-prussiate of potash, 

 after yielding an immense quantity of gases, chiefly azote, left 

 a siliceous combination with the residuum of the triple salt, 

 which was partly a simple hydro-cyanate of potash undecom- 

 posed. How can we imagine this compound with silica to be 

 formed, if potassium alone be present; or how does not the 

 silica expel the cyanogen from its combination ? 



When the anhydrous ferro-prussiate mixed with fused boracic 

 acid was exposed to ignition in a glass tube, the apparatus 

 always burst from the frothing up of the materials. With 

 regard to the gaseous products of this salt by the action 

 of ignited oxide of copper, the results have differed widely. 

 Mr. Porrett found 4 of carbonic acid to 1 of azote ; M. 

 Berzelius obtained the proportion of 3 to 2 ; and M. Robiquet 

 that of 2 to 1. These differences seem to proceed from the 

 mode of operating, and the period of the process at which the 

 examination is made. If the heat be applied slowly and suc- 

 cessively, a pretty steady proportion is obtained during the 

 whole course of the operation ; but a part of the carbonic 

 acid is retained by the potash. When the heat is applied sud- 

 denly over the whole extent of the tube, the ratio of the car- 

 bonic acid to the azote is extremely variable. No precise 

 analytical results can be inferred from the experiments with 

 peroxide of copper, for the above reasons. But M. Robiquet 

 has judiciously combined the two actions of oxide of copper 

 and boracic acid on the anhydrous prussiate. This experiment 

 completely succeeded. He mixed together 1 gramme of an- 

 hydrous prussiate, 2 gr. of fused boracic acid, and 20 gr. 

 pf oxide of copper. The whole was introduced into a strong 

 tube of small diameter. To this tube he joined a second, 

 containing muriate of lime exactly weighed, from which a 

 third, conducted the gases under the glass receiver. After 

 making the requisite rediictions in the gaseous products, he 

 had obtained : 



Azote 0.2297 ? ^ n ^om 



Carbon Q^^^^^\or C^^x.ogenQA2<5\ 



a quantity which, combined with the proportions of iron and 

 potash found in one of his preceding experiments, gives for one 

 grain of prussiate, 



Cyanogen 0.429 1 ^ 



Iron , 0.1 442 C forming a sum too great by 0.0713. 



Potash . 0.4980^ 



1.0713 



