Chemical Contributions. 349 



pherical shells bound together by flanches, it is a hollow sphere in a 

 single piece. The only defect attaching to it seems to be that the 

 mercury is applied directly to the surface of the brass, and although 

 tliat surface is not of such a nature that any _§-rea^ action between the 

 two is to be apprehended, there is danger that there will be some, and 

 that the screw or some other part of the instrument that is brought 

 into contact with the mercury will be corroded. Instead then of pour- 

 ing the mercury directly upon the brass, a neater and better way will 

 evidently be to put it into a tube of glass, or iron, having a hole cut in 

 its side. The long ascending tube will dip into this, the elastic force 

 of the steam be exerted through the opening, and the usual results 

 obtained. 



On the preparation of the substance commonly called phosphuret 

 of lime. 



Three or four different methods of procuring phosphuretted hy- 

 drogen are given in the books. 1 . By means of phosphuret of lime 

 which is to be thrown in small lumps into water acidulated with mu- 

 riatic acid. 2. By pouring sulphuric acid into water containing phos- 

 phorus, cut into small pieces and finely granulated zinc. 3. By drop- 

 ping phosphorus into a retort previously filled with a hot solution of 

 pure potassa. To secure the retort from fracture, Dr. Coxe recom- 

 mends that it be fastened to a triangular block of wood. It appears 

 impossible that any one who has tried the three methods and compared 

 them, should consent to employ either of the two last, if he has any 

 tolerable means of supplying himself with the phosphuret of lime. 

 Unless other persons have succeeded better than myself in regard to 

 scalding their fingers with the hot liquid — ^breaking their retorts, and 

 especially as to the quality of the gas procured by the method of Dr. 

 Coxe, it must give them little satisfaction. That it should have been 

 adhered to so long, is I presume to be attributed to the want of 

 some good method of procuring the phosphuret. 



We are directed to take a green glass or porcelain tube closed at 

 one end, eighteen inches long, and an inch in diameter ; to cover it 

 carefully with clay lute containing a little borax ; put an ounce of 

 phosphorus into its lower end ; fill it with small pieces of quicklime; 

 place it in a furnace, with the end containing the phosphorus protru- 

 ding ; heat it to redness, and then draw the cool part into the fire so 

 that the phosphorus may be volatilized, and pass over the heated lime. 

 Instead of the tube I employ two Hessian crucibles, some of the 

 inner members of a nest. The larger of the two has a hole bored 



