XXX Transactions of the Royal Society of Sontli Africa. 
The collection represents specimens, which, solely because they possessed 
crystal faces, were set aside during the sorting of tantalite from dehris 
obtained by blasting. 
Apparently two distinct varieties of tantalite are represented which, 
whilst exhibiting a general similarity of crystal form, consistently differ 
from each other in certain crystallographic details, in specific gravity and 
other physical characters, and presumably in chemical composition. 
Attention is drawn to the fact that if the form u (133) occurring on the 
crystals of tantalite be regarded as the unit pyramid (111), this would 
accordingly necessitate turning the crystals round their vertical axes through 
90 degrees in order to read them correctly as orthorhombic crystals. 
If that be done the crystals of tantalite exhibit not only a very close 
resemblance in form and habit to the figured crystals of polycrase and 
euxenite, but the crystallographic angles also approximate very closely to 
those recorded for both polycrase and euxenite. 
Polycrase and euxenite are niotates and titanates of yttrium, erbium, 
cerium and uranium, and it is suggested that they may be isomorphous 
with tantalite, and that the intergrowth of very minute quantities of these 
minerals with the tantalite may account for the radioactivity of the latter 
mineral. 
" Colour and Chemical Constitution. Part Y: The Yellowness of Certain 
Phthaleins when Acid." By James Moie. 
Phenolsulphonephthalein, on account of its high ionisation, does not form 
a colourless ring-lactone like phenolphthalein, but remains yellow when 
acidified : it is really the orthosulphonic acid of benzaurine (which shows 
similar colour changes). Benzaurine parasulphonic acid and benzaurine- 
carboxylic methylester (" phenolphthalein methylester '*) have now been 
made and found to possess the same property of yellowness in acid solution, 
lactone-formation being excluded in both cases. The latter substance is 
coloured pink by bicarbonates, and not bleached by excess alkali. 
" Colour and Chemical Constitution. Part YI : The Ultra-violet Spectra 
of the Phthaleins." By James Moie. 
A discussion of Howe and Gibson's discovery of violet and ultra-violet 
absorption-bands in alkaline phthaleins. These have frequencies which are 
1^ times and twice those of the visible band. It folio vfs that the fundamental 
vibration of alkaline phenolphthalein is still unobserved, being in the infra- 
red at X 11090 (frequency 9*02) on the usual scale. The visible band in the 
green is its 1st harmonic, and the other two are its 2nd and 3rd. The 
bands of phthaleins in II2SO4 solution described in Part I (1917) are due 
to the violet 2nd harmonic " loaded " with II3SO4 and so brought up into 
the green. Similar " loading " effects are observable in other heavy solvents. 
If y is the visible II0SO4 frequency, and x is the violet alkali frequency, then 
