
v 

TRANSACTIONS OF THE SECTIONS. 37 
At last the author tried what kind of precipitate some of the most famous mineral 
springs of Germany would form, if they at the boiling-point acted upon sea water. 
Thus he obtained from the water of Selters— 
Carbonate of lime .....cacceceseese 86°55 
Carbonate of magnesia............... 13°45 


- 100:00 
From the water of Pyrmont— 
Carbonate of lime ...........0085 ve 84:38 
Carbonate of magnesia ........... . 512 
Protoxide of iron ..........ceseeeeeaee 10:50 
100°00 
The oxide of iron in the experiment was of course precipitated as peroxide of iron, 
and from that the carbonate was calculated. 
From the water of Wildungen— 
Carbonate of lime ..... eawuieceere ao Sele 
Carbonate of magnesia ............ 7°88 
100-00 
On a New Method of ascertaining the Quantity of Organic Matter in Water. 
By Prof. ForcoHaMMer. 
The test which the author applies is hypermanganesiate of potash or soda, which 
he prepares in this way ; he heats the hydrate of potash or soda with chlorate of pot- 
ash and peroxide of manganese, according to the method of Wohler. After heating, 
the salt is thrown into water, and so much diluted muriatic acid is added that it 
assumes a bluish-red colour, upon which carbonic acid gas is led through, until the 
colour has become bright red and the «manganesiate of potash completely converted 
into hypermanganesiate. The liquid must be cleared, either by allowing it to deposit 
all the oxide of manganese, or by filtering it through asbestos. This liquid may be 
kept for a very long time unaltered in a glass vessel with a glass stopper. The next 
process is to ascertain the strength of the test, which is done by taking any deter- 
mined measure of it, mixing it with water and a little alcohol, and then heating it. 
All the manganese is thrown down, and after being washed and exposed to a strong 
red heat, it is the compound oxide of manganese, 3Mn+ 40. 
This test is now applied in such a way, that, for instance, one pound of the water 
which is to be tried is mixed with a small quantity of the test and boiled; if the colour 
has disappeared, another quantity is added, and the liquor again boiled, until, in going 
on in that way, the red colour of the liquid does not disappear any longer. After that 
it is allowed to cool, and then the quantity of hypermanganesiate of potash, which has 
not been decomposed for want of organic matter in the water, is determined by com- 
paring its colour with distilled water, to which have been added very small deter- 
mined quantities of the test solution. If the quantity of the test which thus is added 
in excess is subtracted from the whole quantity which has been used, the real quan- 
tity of decomposed hypermanganesic acid is determined, and thus also the quantity 
of organic matter itself. ‘This method is liable to one fault, viz. that the nature of 
the organic matter may be different, and accordingly require different quantities of 
the test liquor to be decomposed. But the organic matter which generally occurs 
in water is approaching almost always to humic acid, and thus the determination of 
the organic matter is practicable. As to that part of the organic matter in water 
which contains nitrogen, the author thinks that he has found out a method to de- 
termine it by itself; but not having yet finished his experiments on that point, he 
must leave it out of the question. 
Water taken from a greensand spring about twelve miles from Copenhagen, con- 
_ tained so little organic matter that 1 pound only required 6 measures of a test solu- 
tion, of which 100 measures contained the manganese of 0°526 of the double oxide 
of manganese, while water taken from a lake which communicates with a peat moss, 
required for 1 pound 74 measures of the same liquor, Prof, Forchhammer, con- 
