198 Richards and Palmer—Antimony Tannate. 
The weighed quantity of the substance in which the tannic 
acid is to be estimated is taken in sufficient quantity to allow 
of, at least, three aliquot parts, each portion of 50 to 100 ce. 
containing ‘100 to 300 grams of tannic acid. Acer: the solu- 
tion, made by doa with water, is made up to a known 
bulk, three or four portions are measured out and set in a water 
bath to be heated to 50° or 60° C. The standard solution of 
r emetic contains 6-730 grams per liter of the C,H,KSbO, 
a ined at 100° C. 1 ce, is considered to correspond to 010 
grams per liter for the same valu 
The estimation is facilitated by. obtaining a maximum and a 
minimum point at the first reading, as one portion is settling 
while the other is being treated; therefore tartar emetic is 
added from a burette to one portion in cn of the probable 
quantity required, and to another in less amount. ‘lhe anti- 
mony tannate is then Sronipitaien by the pasate number of 
cubic centimeters of ammonium acetate, and allowed to settle. 
A drop of the clear liquid is added to a drop of sodium hypo- 
ite dene, on a hot tage plate, and if the tartar emetic has 
been added in excess, the deep orange color of the antimony 
sulphide will at once appear. When this point is reached by 
successive additions of the standard solution to the minimum 
portion, we add to a third portion the oan quantity, and 
test the clear liquid as a check on the loss occasioned by taking 
out several drops. 
e have found it easier to carry the titration to a decided 
orange tint, and to subtract ‘5 c.c. of tartar emetic solution for 
100 c.c. of liquid, rather than to pe to seize the first faint tinge, 
as most of the ean to be titrated contain coloring matter 
_ oi a yellowish or reddish tint, but not an orange color. 
states that neither gallic acid = the coloring ee 
Sonenied 3 in certain substances affects the results. is seem 
to be true so far as gallic acid is Reo but the dacucan 
of the relation of the coloring matter to the precipitate, together 
with the results of our titrations and combustions of antimony 
tannate from hemlock bark, oak bark, sweet-fern leaves, etc., 
must be reserved for a future paper. 
Massachusetts Institute of Technology, Woman’s Laboratory, July, 1878. 
