848 
ON A SPECIES OF IPOMCEA, AFFORDING TAMPICO JALAP. 
the dish. The experiment appears to show conclusively that an amalgam of 
hydrogen and mercury can be formed, and that hydrogen is really a metal. It 
would also throw some doubt upon the existence of the amalgam of ammonium 
and mercury, and offer an explanation of that compound on the basis of its 
being the same amalgam of hydrogen and mercury that is prepared in the way 
now pointed out by Dr. Loew. The smell of escaping ammonia must be traced 
to some other source than the existence of that radical in combination with 
mercury.— 4 Chemical News ’ from the ‘ Scientific American. 1 
Cryptophanic Acid, the Normal Free Acid of Human Urine. 
At a recent meeting of the Chemical Society Dr. Thudichum described a new 
organic acid,—cryptopbanic acid, the presence of which he considers the cause 
of the acid reaction usually exhibited by urine. 
It is extracted somewhat as follows :—“ The urine is rendered alkaline with 
milk of lime and filtered, it is then acidified with acetic acid and evaporated 
down to a syrup ; after standing some time, the syrup is drained from the crys¬ 
talline deposit and is mixed witfi strong alcohol. On shaking, a dark coloured 
precipitate forms, from which the fluid is decanted. 
The precipitate, which is the impure calcium salt, is washed with alcohol, dis¬ 
solved in a small quantity of water, and filtered through calico. On again 
adding alcohol, it is reprecipitated. By repeated solution and reprecipitation 
in this way it may be obtained nearly pure. 
To complete the purification, the calcium salt is dissolved in water, mixed 
with solution of lead or copper acetate, the liquid filtered from the impure basic 
salt, and the clear solution mixed with alcohol. Pure lead or copper cryptopha- 
nate is then precipitated. To obtain the acid, the lead salt may be decomposed 
with an equivalent quantity of dilute sulphuric acid, or the copper salt by sul¬ 
phuretted hydrogen. 
The acid is a colourless gummy mass, soluble in water; it decomposes carbo¬ 
nates with effervescence. The aqueous solutions of the earthy salts give, 
amongst other reactions, with mercury nitrate, a voluminous white precipitate. 
The ordinary estimation of urea by Liebig’s process is thus shown to be liable to 
errors, and to require a correction for cryptophanic acid, which has probably 
increased all values for urea by from 5 to 10 per cent. Cryptophanic acid may 
be considered a dibasic acid of the formula C 5 H 9 N0 5 ; or it may be represented 
as tetrabasic with the formula C 10 H 13 N 2 O 10 . In that case, the metallic salts, 
of which a considerable number are described in the original paper, will have 
the general formula C 10 H 14 M' 4 N 2 O 10 . Many of the salts are soluble in water, 
but some, as those of silver, lead, and mercury, are insoluble. 
ON A SPECIES OF IPOMCEA , AFFORDING TAMPICO JALAP. 
BY BANIEL HANBURY, ESQ., E.R.S., F.L.S. 
Two centuries and a half have elapsed since jalap, the tubercle of a convolvulaceous 
plant of Mexico, was introduced into the materia rnedica of Europe. The botanical 
origin of the drug long remained unsettled, evidence of which exists in the fact that two 
plants, neither of which yields jalap, have in succession received, and still retain the 
specific name Jalapa. The veritable source of jalap, however, was brought to light 
between the years 1827 and 1830, in which latter the plant was described by Wenderoth 
as Convolvulus purga. In 1833 it was figured by Hayne under the name of Ipomcea 
purga; but in 1839 it was transferred, on account of its tubular corolla and exsert sta¬ 
mens, to Choisy’s genus Exogonium. As this genus has been recently united to Ipomcea 
by Dr. Meisner, it appears best to return to the name proposed by Hayne, and to call 
the true jalap-plant Ipomcea purga. 
