434 
POPULAR SCIENCE REVIEW. 
Chianti, 2*020 ; common green glass, used for Rhenish, Bordeaux, Cham- 
pagne, &c., 3*202 ; yellow-brown glass, used for Bordeaux, Madeira, Malaga, 
&c., 3*387 ; and the red-brown, used for Rhenish, Ruster, Rohitscher, &c., 
4*888. — The Chemical News, 1878, xxxviii. p. 5. 
The Solubility of Platinum in Sulphuric Acid. — Scheurer-Kestner has con- 
tinued his inquiry into the solubility of this metal in concentrated sulphuric 
acid, and finds that while the action of a 95 per cent, acid is a very marked 
one it becomes still more notable when the concentration exceeds that cor- 
responding to the monohydrate. With the hope that platinum apparatus 
might be adapted to the manufacture of Nordhausen acid on a large scale, 
sodium bisulphate was fused in a glass retort lined with platinum foil, and 
the vapours were condensed in stone vessels. A number of experiments 
were made in this way with an apparatus the platinum of which weighed 
5 kilog., and it was found that for every 100 kilog. of acid distilled 100 
grammes of metal were dissolved in the sodium sulphate. In the earlier 
experiments 100 kilog. of 94 to 99 per cent, acid dissolved 1 to 8 grammes 
of metal. — Comptes rendus, 1878, lxxxvi. p. 1082. 
Inve?’tin. — This, the inverting constituent of yeast, to which Donath 
gave the above name, has been submitted to a long investigation by Barth 
( Per . Deut. Chem. Gesell., 1878, xi. 474). To obtain it he coarsely pul- 
verises fresh compressed yeast and dries it at temperatures not exceeding 40° 
until it can be rubbed to powder between the fingers ; it is then heated to 
100° or 105° for six hours, mixed with water in considerable quantity, and 
after having been allowed to stand for twelve hours at 40° the insoluble por- 
tion is removed by filtration. The filtrate, which has a yellowish hue, is 
poured into six times its volume of alcohol containing 95 per cent. ; this 
-causes the formation of a white flocculent precipitate, which when violently 
agitated becomes granular, and then may easily be collected on a filter. The 
albuminates which are likewise thrown down by the alcohol can be removed 
by treating the precipitate with a limited amount of water, when they re- 
main undissolved as a gelatinous mass. A second treatment with alcohol 
yields the ferment in a pure state. Two grammes of the ferment are obtained 
from 500 grammes of yeast. Invertin is a white powder, which dissolves 
in water, forming a yellowish-brown solution ; this is not rendered turbid 
when boiled with acetic acid and salt, and is thus shown neither to be an 
albuminate nor to contain one as an impurity. When boiled with dilute 
copper solution and sodium hydrate it does not strike a violet colour ; this 
indicates an absence of peptones. After heating some for a long time with 
sulphuric acid no leucin could be found. Analysis showed invertin to con- 
tain 22 per cent, of ash, consisting of potassium, calcium, and magnesium 
phosphates. If the inorganic constituents be excluded, the ferment contains : 
carbon, 33*9 per cent. *, hydrogen, 8*4 per cent. ; nitrogen, 6*0 per cent; sul- 
phur, 0*63 per cent. ; and oxygen (by difference), 41*17 per cent. The activity 
of invertin appears to be dependent on the degree of concentration of the 
sugar solution, and is proportional to the amount of ferment present ; it 
reaches its limit in about forty hours. One part of invertin can produce 
760 parts of inverted sugar. 
Tinfoil and Tinplate. — Kopp and Engel have recently examined specimens 
of the tinfoil used in packing French chocolate. Traces only of lead were 
