220 Prof. Davy on some further Applications of 
water; pour it into the flask which was used in preparing the 
two standard solutions, and having filled up with water to the 
mark in the neck, mix the solution thoroughly; and before each 
time that any of the chloride of lime is taken out, shake well 
the contents of the flask. 
Measure out into a beaker-glass, by means of the two little 
bottles, 100 divisions of the chloride of lime solution, and 50 of 
the standard solution of ferrocyanide; and having mixed them 
well together, add some hydrochloric acid to dissolve the preci- 
pitate formed and acidify the mixture strongly ; and having 
mixed the whole well, pour from the burette slowly the standard 
solution of bichromate (stirring well all the while) till a drop 
taken from the mixture and brought in contact with a drop of a 
very weak solution of perchloride of iron produces a yellowish- 
brown colour, as already noticed. Then read off the number of 
divisions of the standard solution of bichromate which was 
necessary to produce this effect; and this being deducted from 
50, gives the per-centage by weight of chlorine. 
For the standard solution of ferrocyanide having been made 
so that the 10000-grain measures should be equivalent to 100 
grains of chlorine, and as every division of the burette equals 10 
grains, each of these divisions of the ferrocyanide solution con- 
verted into ferrideyanide will indicate O°1 grain of chlorine. 
Again, the 100 divisions of the solution of chloride of lime 
represent lO grains of that substance, and we want to know 
how many divisions of the ferrocyanide solution its chlorine has 
converted into ferridcyanide. This is readily ascertained by 
the bichromate solution, which has been so graduated that 
each division represents a division of the ferrocyanide solution. 
So that to determine the per-centage of chlorine we have only 
to deduct, as before stated, the number of divisions of the 
bichromate solution employed from the 50 of the ferrocyanide 
solution, and the difference gives us the per-centage of chlorine 
by weight in the sample; thus in four experiments 50 divisions 
of the ferrocyanide solution, mixed with 100 divisions of the 
solution of chloride of lime, required 18:5 divisions of the bi- 
chromate solution to convert the whole of the ferrocyanide em- 
ployed into ferrideyanide; this number, taken from 50, leaves 
31°5 divisions of ferrocyanide, which were-converted into ferrid- 
cyanide by the chlorine of the chloride of lime; and as each 
division represents 0-1 grain of chlorme, 31°5 will be equivalent 
to 3°15 grains of chlorine, which is the amount contaimed in 10 
grains of the sample ; consequently 100 grains will contain 
31°5 grains of chlorine, which is the same amount as is obtained 
by simply deducting the number of divisions of bichromate solu- 
tion employed from 50 of ferrocyanide used in the estimation. 
