ASTRINGENTS.
5°5
Sp. gr. at Tannin
15° C,=59° F. per cent.
1*0000 o-o
1*0004 . 0*1
1*0008 0*2
1*0012 0*3
1*0016 o*4
1*0020 0*5
1*0024 o*6
1*0028 0*7
1*0032 o*8
1*0036 0*9
1*0040 1*0
1*0044 1-1
1*0048 1*2
1*0052 1*3
1*0056 1*4
1*0060 1*5
1*0064 i*6
1*0068 1*7
1*0072 i*8
1*0076 i*g
1*0080 2*0
1*0084 2*1
1*0088 2*2
1*0092 2*3
1*0096 2*4
1*0100 2*5
Sp. gr. at
Tannin
1°C.=59“ F.
per cent.
1-0104
r*oio8
.. .. 2*7
roii2
.. .. 2*8
1*0116
.. .. 2*9
1*0120
.. .. 3'°
1*0124
.. .. 3-1
1*0128
.. .. 3' 2
I*OI32
•• -• 3'3
1*0136
•• •• 3'4
I*0I40
1*0144
.. .. 3'6
1*0148
•* •• 3'7
1*0152 .. ..
•• .. 3-8
1*0156
.. .. 3*9
1*0160
.. .. 4*0
1*0164
.. .. 4*x
1*0168
.. .. 4*2
1*0172
• • • • 4'3
1*0176
• • • • 4‘4
1*0180
.. .. 4*5
1*0184
.. .. 4*6
rox88
• • • • 47
I’Oiga
.. .. 4'8
1*0196
1*0201
Persoz prepares a standard solution of tannin, containing 10 grms. perlitre, and another solution of 8 grms. tin crystals and 2 grms. sal-ammoniacin 1 litre of water. A number of glass cylinders are provided, graduated incubic centimetres, and holding each 200 c.c. To perform an analysis he putsinto two cylinders 100 c.c. of the tin liquid each. To the first he addsthen 100 c.c. of the standard tannin solution, and to the second 100 c.c. ofthe extradt of 1 grm. of the sample of astringent material under examination.Both cylinders are then, after well stirring up, set aside for twelve hours, whenthe volumes of the precipitates are read by the graduation on the glass, andthe amount of tannin per cent is thus calculated.
Risler-Beunat colledts the precipitate formed on adding the tin solution tothe extradt of an astringent, filters, washes, dries at 212° F., and weighs. Theresidue is then ignited and peroxidised by aid of nitrate of ammonia. Theperoxide of tin thus obtained is weighed, the amount of protoxide which itrepresents is found by calculation, and this being dedudtedfrom the first foundweight the remainder is tannin.
According to Dr. Stenhouse, the tannic acid present in valonia does notyield, on being boiled with dilute sulphuric acid, gallic acid and sugar, but,instead of the former, a reddish-brown substance, which is sparingly solublein alcohol. The tannin of divi-divi also differs from that of galls, as is alsothe case with the astringent piinciple of myrobalans, while sumac contains