58 REPORT—1850. 
could nevertheless not detect any appreciable quantity of carbonic acid; addition of 
acetic acid to the residue left on evaporation of the blood serum. 
Another source of error in determining the quantity of carbonic acid in blood, is 
found in the greater power of absorbing carbonic acid which acetic acid possesses in 
comparison with that of water. According to Mulder, 100 vol. of acetic acid of a 
specific gravity of 1-070 absorbs 350 yol. of carbonic acid. 
: Acetic acid of 1:064 ,, 900 ἐὰ 
᾿ ΓΙ Τὺ ᾿ 
᾿ ΤΟΙ 110 ἢ 
The author disagrees with Liebig, who, as it is well-known, explains the fact that 
blood absorbs much carbonic acid by the presence of the tribasic phosphate of soda in 
blood, with which salt, according to him, carbonic acid enters into chemical combi- 
nation, and mentions some experiments, which are intended to prove that no chemical 
change takes place when carbonic acid is passed through a solution of tribasic phos- 
phate of suda; on this occasion Mulder found that tribasic phosphate of soda simply 
possesses a greater power of absorbing carbonic acid than water. This however he 
found to be the case with other salts likewise; phosphate of lime particularly is men- 
tioned by the author as a salt which absorbs half more of carbonic acid than water. 
For these reasons Prof. Mulder considers it illogical to ascribe solely to phosphate of 
soda, a function in blood which it shares with several other combinations, both or- 
ganic and inorganic, which are found in blood. 
On a new and ready Process for the Quantitative Determination of Iron. 
By Dr. Freverick Penny, Professor of Chemistry in the Andersonian 
Institution, Glasgow. 
In this paper the author recommends the employment of the chromate and bichro- 
mate of potash for the estimation of iron in the common ores of the metal, and espe- 
cially for the analysis of the clay-band and black-band ‘ironstone of this country. 
He was led to the application of these salts in the course of certain investigations 
upon the materials and products of the manufacture of alum from alum-shale, in 
which he was much retarded by the want of a ready method for estimating the oxides 
of iron, After trying various modes, and also Marguerite’s process with the per- 
manganate of potash, he decided on the chromates of potash, which give very exact 
results, and possess the great advantage that a much larger quantity of material may 
be operated upon than can be conveniently treated by the usual methods. For prac- 
tical purposes, he says, the bichromate is to be preferred. The process requires no 
other apparatus than that commonly used for Centigrade testing, which is familiar to 
all persons engaged in chemical pursuits. It may be easily and rapidly executed, 
occupying only a fraction of the time required for the process of estimating iron by 
precipitation as the sesquioxide ; and it is not interfered with by the presence of alu- 
mina and phosphates, which usually exist in the ore. The method is based upon the 
well-known reciprocal action of chromic acid and protoxide of iron, whereby a trans- 
ference of oxygen takes place, the protoxide of iron becoming converted into sesqui- 
oxide, and the chromic acid into sesquioxide of chromium. The following equation 
will serve to exhibit the general nature of this reaction :— 
2CrO,46FeO=Cr 0+3Fe’0. 
The following is an outline of the mode of operating in the case of clay-band and 
black-band ironstone. The test solution of bichromate of potash is first prepared by 
putting into a common alkalimeter 44-4 grains of the salt in fine powder, filling to 
zero with tepid distilled water, and agitating until the salt is dissolved and the solution 
is of uniform density throughout. 100 grains of the ironstone, previously pulverized, 
are dissolyed in hydrochloric acid, and the solution diluted with water, and filtered in 
the usual manner. To this filtered solution the test-liquor in the alkalimeter is now 
added, until, on testing a portion of the mixture with red prussiate of potash, a blue 
colour is no longer produced, but a reddish tinge communicated. The operation is 
then finished, the number of divisions of test-liquor consumed carefully read off, and 
this number divided by two gives the amount per cent. of metallic iron in the ore, 
Dr. Penny gave the results of numerous experiments made with pure metallic iron, 
