Technical Chemistry. 283 
by side. In case of the former, the point of neutralization (or rather of 
supersaturation,) is shown by a prompt and decisive change from a tint 
in which orange predominates, to one in which this disappears and violet 
is most marked. In presence of carbonic acid the change is somewhat 
trifle less of it will be found needful to neutralize a given volume of acid, 
that 10 c.¢. SO, = 7°66 and 7-67 a so" 5 
not expelled, 10 ¢.c. SO, = 7°68 and 7-7. These results are as good as 
identical, In standarding the much weaker acid used for the nitrogen 
determination above mentioned, he obtained for it a value slightly too 
low when O, was not removed, 0°53 grm. NaO Co, required in this 
case but 53°05 ¢. ©. SO, instead of 53°155 as in the other instances, 
This is a very slight difference and not appreciable perhaps with ordinary 
deutralized b 
independent of the small amount of carbonic acid that can come from 
@ permanence of the color also allows several titritions to be 
compared directly together. 
A third advantage of cochineal is, that its solution, prepared as above 
: may be preserved indefinitely in closed vessels, without decolor- 
ation or alteration. 8. W. J. 
3. On the solubility of Sulphate of Lime in chlorhydric acid.—In this 
Laboratory it has long been the custom to bring into solution for analyt- 
aan eurposes gypsum, so-called super-phosphate of lime and other sub- 
trated 
dilute, and therefore a saturated solution of the salt in the latter is co- 
‘ously precipitated by the addition of fuming chlorhydric acid as well 
that of water. 8. W. J. 
. eee Cuemistry. B 
3. Webster's process for producing Oxygen Gas.—J. Wesster of Bir- 
™ingham (England), has taken out a patent for obtaining oxygen (and 
Céttain other products,) from nitrate of soda and oxyd of zine, or per- 
°xyd of iron, subjected to a low red heat in close retorts. @ gaseous 
