334 EXPERIMENTS ON THE RELATION 
touch of the finger breaks them across. Digested in pure ni- 
tric acid somewhat dilute, the segments only partially dissolve, 
bits of muriate of silver, of their own shape, being left in the 
liquid. . 
The ignited copper turnings, after experiencing the action of 
sal ammoniac, are found to have lost also their original lustre, 
and have acquired a dull brown colour. Digested in water, a 
liquid muriate is obtained, which gives the characteristic brown 
precipitate with prussiate of potash. 
The most considerable of my experiments with turnings was 
made with the tube of Reaumur’s porcelain, which, as it con- 
tains no oxide of lead, is not liable to any ambiguity on this. 
score, and being capable of sustaining a very high heat with- 
out fusion, permitted me to obtain very satisfactory results in- 
deed. 
Thirty grains of recently heated sal ammoniac being put 
down to the sealed end, 200 grains of bright turnings of very 
pure soft iron were introduced over it, so as to occupy six 
inches of the tube. The glass tube above described, was at- 
tached by the elastic gum collar. The part holding the iron 
being brought to bright ignition, the sealed end of the tube 
was advanced by degrees almost imperceptible. As soon as 
the salt began to exhale, moisture began to condense in the 
glass tube, though none ever appeared prior to heating the sal 
ammoniac. The evolution of gas was much more copious: 
than in any of the experiments with the other metals. When 
allowed to escape through the quicksilver into the air, it exhi- 
bited the dense cloud, and had the odour of muriatic acid. 
Received into a tube over mercury, and then exposed to the 
action of water, ;4, parts of the volume were absorbed, which 
on trial were found to be pure muriatic acid. The remainder 
was a mixture of azote and hydrogen, in the proportions very 
nearly 
