June 22, 1872.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
1029 
Fe 2 Cl 6 + 3ZnC0 3 + 3H 2 0 = 
Fe 2 (HO) 6 + 3ZnC! 2 4- 3C0 2 
and PbCl 4 + 2ZnC0 3 -f 2H,0 = 
Pb(H0) 4 + 2ZnC) 2 -f 200 2 . 
By digesting the solution on an excess of metallic 
zinc, as the Pharmacopoeia directs, no lead will be 
taken up. 
Evaporated until watery vapour ceases to be 
evolved the solution leaves the zinc chloride as a 
colourless syrup, which solidifies on cooling. It may 
be made to crystallize from a very concentrated 
solution. 
[§ Colourless opaque rods or tablets very deliques¬ 
cent and caustic, soluble almost entirely in water, 
alcohol and ether.] 
The white flocculent precipitate generally left 
when chloride of zinc is dissolved in water is oxy¬ 
chloride. For the detection of impurities the same 
tests may be employed as with the other salts of 
zinc. 
Chloride of zinc enters into direct combination 
with ammonia, NH 3 and also with alkaline chlorides. 
Zixci Oxiduu. —ZnO. Carbonate of zinc is heated 
to redness in a crucible. Carbonic anhydride and 
water escape, leaving the oxide. 
ZnC0 3 2Zn(H0) 2 H 2 0 =: 3Zn0 + C0 2 -j-3H 2 0. 
Oxide of zinc is deep yellow whilst hot, but be¬ 
comes nearly white on cooling. It is sometimes 
made by submitting the metal to distillation in a 
current of air. The oxide thus obtained is very pure, 
but liable to contain particles of metal. 
Zixci Sulphas. —ZnS0 4 .7H 2 0. Zinc is dissolved 
in diluted sulphuric acid, and when the acid is satu¬ 
rated, the solution is treated with chlorine and car¬ 
bonate of zinc for the purpose of removing iron. A 
small quantity of chloride of zinc is thus introduced 
into the solution, but it is too minute to interfere 
with the purity of the crystals which are obtained 
on evaporation. 
2FeS0 4 + CL 4- ZnC0 3 . 2Zn(HO) 2 . H 2 0 = 
Fe 2 (HO) 6 + ZnCl 2 + 2ZnS0 4 + C0 2 . 
Sulphate of zinc is isomorphous with and closely 
resembles sulphate of magnesium. From that salt 
it is readily distinguished by giving white precipi¬ 
tates with ferrocyanide of potassium and sulphide of 
ammonium. 
Sulphate of zinc is soluble in about two and a half 
times its weight of water; the solution has an acid 
reaction. The crystals lose six molecules of water 
by the heat of a water-bath, but, like the other 
sulphates of the same class, it retains the seventh 
molecule even at much higher temperatures. Im¬ 
purities would be detected by the tests already given. 
[Zinci Acet.] 
PREPARATION OF A VERY ACTIVE CANTHARIDAL 
PLASTER. 
by rnoF. g. diiagexdorff (Dorpat, Russia)'. 
Apothecaries frequently complain that some cantha- 
rides do not furnish an active blistering plasterthat 
the same furnish, even when treated with acetic ether, 
an extract so poor in cantharidin, that with its aid no 
good Drouott’s blistering tissue can be produced. In 
most cases the opinion is expressed that the flies contain 
too small a percentage of cantharidin. My experience 
teaches me to discredit the latter opinion. It is possible 
to obtain good preparations even from such apparently 
poor cantharides, it being only necessary to thoroughly 
extract the cantharidin they contain. 
A few observations show how poorly this i3 commonly 
accomplished. According to my experience the amount 
of cantharidin in Spanish flies varies from 0-27 to 0A 
per cent. The coating of a vesicating tissue 20 c. m. 
long and twelve wide requires about 25 grin, plaster 
substance, containing usually about 6 grin, powdered 
Spanish flies, furnishing at least O'OIG cantharidin. 
0-00002 grm. cantharidin suffice for a blistering surface 
of a square centimeter, or 0-0048 grm. for 240 square 
centimetres, or less than one-third of the smallest 
quantity that may be considered present in the plaster. 
Mechanical causes may partly be found to be the ones 
that prevent a thorough action of the plaster. A plaster 
of poor adhesiveness, not being in close contact with the. 
epidermis, does not act because that close contact is 
wanting, which is necessary for the absorption of tho 
cantharidin. It is also a mistake of several pharmaco- 
poeias to permit the use of coarsely-powdered cantharides, 
the quantity of cantharidin in which is not uniformly 
distributed in the plaster, even if the powder is heated 
for a long time with the oil. 
Other causes, unnoticed heretofore, also weigh heavily 
in this direction. The cantharidin is present in the 
Spanish flies in several different combinations, in which 
it is firmly held. This fact I have mentioned already 
in my “ Contributions to Toxicological Chemistry,” on 
the different behaviour of flies towards various solvents. 
Cantharides with about 0-3 per cent, of cantharidin 
yield to water, even after repeated boiling with fresh 
portions of the same, only about half of their cantharidin, 
while the remainder is only yielded to potassa lye. In 
the same manner, alcohol, chloroform, and ether dissolve 
only 30 per cent, of the blistering substance. If all the 
cantharidin is to be extracted, bases like potassa or soda 
must be employed, which form easily soluble salts with 
the cantharidin. Together with Masing, I demonstrated 
years ago that the salts thus formed are energetic blister¬ 
ing agents. During the past two years, reference has 
occasionally been made to our observation, especially by 
Delpech and Guichard, recommending the cantharidates 
of soda and potassa as vesicants. 
Without alluding to this further, I would say that by 
the aid of soda or pottassa the entire amount of cantha¬ 
ridin contained in the flies may be rendered active. The 
finely-powdered flie3 are mixed to a paste with diluted 
alkaline lye of about IT sp. gr., heated in water-bath, 
for twenty-five to thirty minutes, when sufficient muriatic 
acid is added, to have a trifling surplus of the same, and 
the whole mass is dried rapidly in the water-bath. The- 
residue, which we may call “ prepared cantharides,” 
is powdered anew and employed for the preparation of 
the plaster, or for the extract with acetic ether for use- 
upon tissue. The small quantity of potassium or sodium 
chloride present, is in no case injurious. The cantha¬ 
ridin is now present in the mixture in a free state. In 
a drug store in this city, where my proposition has been 
followed, no complaints have been made about the pre¬ 
paration. 
Even for the preparation of the pure cantharidin, the 
above-mentioned process is worthy of attention. As I 
mentioned before, ether, alcohol, etc., dissolves from the 
cantharides, not “prepared,” only a fraction of the can- 
tharidin present .—The Chicago Pharmacist. 
DISTRIBUTION OF ATROPINE IN THE LEAVES 
AND ROOTS OF THE BELLADONNA. 
BY M. LEFOBT.* 
Therapeutists have been long divided in opinion as 
to the relative degree of activity of the parts of the bel¬ 
ladonna plant most used in medicine, namely, the leaf 
* Memoir read before the Parts Academy of Medicine, 
Nov. 21, 1372 (Journ. de Piuu-m. ct de C Inane [1] vol. xv. 
p. 265. 
