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POPULAR SCIENCE REVIEW. 
the crystals escape at both ends ; such cells have been called biforines 
Twenty-three orders of Dicotyledons and nine of Endogense are enume- 
rated as being among those possessing raphides. Dr. Lankester’s paper 
should be consulted by all who are about to undertake the study of these 
crystalline formations. 
CHEMISTRY. 
A new Oxide of Copper has been discovered by H. Rose and described 
by him in “ Poggendorff’s Annalen,” No. 9. His communication, which 
the reader will find given at some length in the Chemical News of Nov. 23, 
shows that, when the protochloride of copper (which is procured by 
adding to the sulphate a solution of protochloride of tin to which hydro- 
chloric acid has been added) is placed while moist in a dilute solution of 
protochloride of tin in hydrate of potassa, the white chloride is changed 
into a green bod}’', which however is reduced to metallic copper if a 
less dilute alkaline tin solution be employed. This green body is a new 
oxide, lower in the series than the familiar sub-oxide, into which latter it 
is converted on access of even a limited quantity of air, and eventually 
into the bluish protoxide. It is exceedingly difficult to obtain the new 
compound, because on the one hand it is very oxidisable, and on the other 
equally reducible to metallic copper. This compound of the metal with 
oxygen has been styled by its discoverer, Quadrantoxide of copper. 
Another Test for Nitric Acid. — At a late meeting of the Chemical 
Society (Nov. 5th) a paper was read by Dr. Herman Sprengel detailing 
the results of his experiments on this subject. He does not consider that 
the ordinary tests, and especially the starch and iodide of potassium, ever 
can be much relied on. His method depends on the formation of 
coloured bodies, which takes place whenever nitric acid is brought in 
contact with certain phenyl compounds. The test-solution consists of 
phenyl one part, water two parts, and sulphuric acid four parts. The 
phenyl is first dissolved in the acid and then the water is added as a 
diluent. The suspected solution is first evaporated to dryness in a water 
bath, and then a portion of the dried residue is moistened with the test- 
solution, -when if nitric acid is present the liquid will assume a brownish 
tint, which becomes yellow on the addition of ammonia. This test is so 
delicate that the one-six-millionth part of a grain of nitric acid may be 
detected by it. The discovery is in part due to Laurent, but the appli- 
cation is wholly Dr. Sprengel’s. The author’s statements were confirmed 
by Dr. Odling’s observations. 
The History of Thallium. — Mr. Crookes continues his investigations in 
this direction, and with what success is showui by his numerous additions 
to the chemistry of this new metal. Among the salts which have been 
recently under observation we may mention those of the chromates , sul- 
phates, carbonates, phosphates , nitrates, and perchlorates , all of which we 
may almost say have been exhaustively treated of. 
Siliciuretted Hydrogen. — This novel and important compound of 
hydrogen and silicon is produced when another new substance, silicide 
