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rorULAR SCIENCE REVIEW. 
unable to find more than two metals in this group which they termed 
yttrium and erbium (which was really Mosander’s terbium). It was there- 
fore generally supposed that there were only two metals in this group, and 
that terbium did not exist. Last year the subject was taken up by Marignac 
and anew by Delafontaine. In the early part of last year they both 
announced that they had found a third substance present besides yttrium 
and erbium, and agreeing well with the properties of the third metal of 
Mosander. 
The new earth, terbia, is of a pure dark orange colour, but on being 
heated in a current of hydrogen, or at a high temperature in the open air, 
it becomes colourless. Its salts are colourless, and have no absorption spec- 
trum. The atomic weight of terbium is 98*5 or 147*7 accordingly as terbia 
is considered to be a monoxide or sesquioxide. The atomic weight of 
yttrium and erbium are 58 and 114 (or 87 and 171 if these oxides are 
regarded as sesquioxides). Delafontaine now announces the presence of a 
fourth and fifth metal in this group which he has termed Philippium (Pp.) and 
Decipium (Dp.) respectively. The new metal, philippium, has an atomic weight 
of about 74 (or 111), and forms a yellow oxide and a series of colourless salts 
far more soluble than those of terbium, which when concentrated give a very 
intense absorption band in the indigo blue, a band not visible in the salts of 
yttrium, erbium, or terbium. The fifth metal, decipium, resembles didymium 
in its properties, but gives three remarkable absorption bands in the blue and 
indigo. Later, Delafontaine has been led to suspect the existence of a sixth 
metal of this group. In the meanwhile, Marignac has announced the dis- 
covery of yet another member of this group which he terms ytterbium (Yb). 
Both its oxides and salts are colourless, and are moderately easily soluble. 
They do not give any absorption spectrum. The atomic weight of ytterbium 
is about 115 (or 172*5 if the earth is a sesquioxide), or nearly that of 
erbium ; but if the existence of this new metal be confirmed, it is probable 
that it will be found that Cleve and Hoeglund’s determination of the atomic 
weight of erbium was vitiated by the presence of ytterbium, and that it 
ought to be below even Bunsen’s value or about 104-5. Chemists will wait 
with some curiosity to learn whether further investigation confirms the ex- 
istence of these numerous additions to the group of cerium and yttrium 
metals. 
The Absorption Spectra of Organic Substances . — At the meeting of the 
Royal Society for January 9, 1879, a paper was read, by Messrs. W. Noel 
Hartley and A. R. Huntingdon, on the u Absorption of the Ultra-Violet 
Rays of the Spectrum by Organic Substances.” The paper embodies a 
research which is likely to throw considerable light on the molecular con- 
stitution of the organic bodies. The normal alcohols of the fatty series are 
remarkably transparent to the ultra-violet rays of the spectrum ; but there 
is an increased absorption of the ultra-violet rays corresponding to each 
increment of CH 2 in the molecule. The acids and the normal ethereal salts 
derived from the alcohols are highly transparent to the ultra-violet rays. 
When, however, the benzene derivatives came to be examined they were 
found to exert an enormous absorption on the extra-violet rays, and when 
dissolved in water they continued to show marked absorption bands even 
when very dilute. The isomeric bodies, containing the benzene nucleus, 
