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 
that surface is not of such a nature that any great action between the 
two isto 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. _ Instéad then of pour~ 
ing the mercury directly upon the brass, a neater and better way-wilk 
evidently be to put itinto 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. aed” 
- 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 satisfaetion. 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. te 
Wo-are directed to take a green glass or porcelain tube closed at: 
one end, eighteen inches long, and. an ineh 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 » 
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 anest. The larger of the two has a hole bored 
