258 Scientific Intelligence. 
earthen tubes surrounded by water, after which, the hydrochloric acid: 
is effectually separated by passing the mixture through water; and fi- 
nally, the chlorine is obtained, and chloride of lime produced by passing 
the residuary mixture into the ordinary lime condenser, where the 
chlorine is absorbed, and the nitrogen and atmospheric ‘air remaining 
are allowed to pass off. Jia 
6. On the Solubility of the Basic Phosphate of Magnesia and Am- 
monia, and on the quantitative determination of Phosphoric Acid and 
Magnesia by means of this salt ; by Dr. R. Fresenius, (Annalen der 
Chem. und Pharm., July, 1845, p. 109.)—Chemists have been careful 
about washing this salt thoroughly, when used as a means of estimating 
magnesia quantitatively, on account of its supposed solubility. But in 
fact, when the salt is washed with water containing ammonia, hardly 
a trace of it will pass through the filter. One part of the ammonio- 
magnesian phosphate requires 44,330 parts of ammoniacal water for 
solution ; which is equivalent to one part of magnesia in 120,760 parts, 
and one part phosphoric acid in 70,000 parts. 
In estimating magnesia, it is well 208 ie have too eras an excess —_ 
ammoniacal salts in solution, and t 
water, until the water that passes Ay leaves no residue when evap- 
orated on a bit of platinum foil. The salt can be made use of as an 
accurate means of estimating phosphoric acid quantitatively, even when 
the acid is in combination with iron or alumina. 
To analyze the phosphate of iron and alumina, first dissolve in mu- 
riatic acid, then add tartaric acid, and lastly, an excess of ammonia, 
until the whole of the precipitate that is first formed is redissolved ; 
now add sulphate of magnesia, when the double salt in question will 
be precipitated—at the expiration of twelve hours, filter, wash with am- 
moniacal water, dry and ignite the filter and its contents, from the weight 
of which the phosphoric acid may now be calculated. In one experiment 
made with an artificial mixture of the phosphates of iron and alumina, 
this method indicated 20°14 per cent., when the quantity calculated to 
be present was 19-91. Jy Lx 
7. The decomposition of Water by Metals, promoted by the presence 
of Acids or Salts ; (Comptes Rendus, July, 1845, p. 37.)—This sub- 
ject has been extensively investigated by M. Mitton, and with highly 
interesting results. The rapidity of decomposition is sometimes in- 
creased a hundred fold, even by a minute quantity of certain salts. 
Pure zine in dilute sulphurie acid, remains with little or no action, but 
on adding a small quantity of certain salts, decomposition commences 
at once, and hydrogen is evolved, though differing in the amount of 
action with the different salts used. Thus, if the action of pure dilute 
sulphuric acid is represented by 1, that of the bichloride of platinum is 
