394. TRANSACTIONS OF SECTION A, 
Case 6; 
When p<1=cos 6, and cos 6= mn + 3 nearly, 
6723-'mni(cos es Pu) = SOUR) Tae C) sin —  +pr(3) sin (¥ *) 
a(n—m) ‘ 
f'r(2) sin(=) eras sh, 
6733-*mi(cos 8}'Q,™(H)P™(H) = — = { T (5) cos 7 +pr(3) cos (+) 
Ome) 
her =2n+1 i y (sin 0-5" 
ise Picton m cos” 8 
and is small. 
By the use of the relation 
J im(2) = Pn=co Pn {cos § Sp 
and its analogue, it may be shown that all the expansions for Bessel functions 
given in a previous paper are special | cases of these. 
The toroidal functions, with 2 + } integral, are excluded from the investigation, 
11, Report on Bessel Functions.—See Reports, p. 33. 
DEPARTMENT OF GENERAL PHYSICS. 
The following Papers were read :— 
1. On Threefold Emission-Spectra of Solid Aromatic Compounds, 
By Professor E. See Reports, p. 129. 
2. The Influence of Electrolytes on Colloidal Ferric Oxide Solutions. 
By E. F. Burton. 
A commercial ferric oxide solution was dialysed in conductivity water, 
and the velocity with which the particles moved in a unit electric field was 
observed from time to time. At first, as the solution was purified, the 
velocity of the particles increased, but as the purification was carried on 
the velocity gradually decreased in almost linear relation with the amount 
of chlorine found in so colloidal solution. 
The influence of a potassium phosphate on the velocity of the 
particles was measured, and was found to be analogous to the action on the 
Bredig copper colloidal ‘solution previously tried by the author (Phil. Mag., 
May 1909). 
A comparison of the coagulating powers of monovalent, divalent, and 
trivalent ions on the colloidal particles indicates that the Linder-Picton- 
Hardy law holds. 
3. Separation of New Radio-aciive Disintegration Products. 
By Dr. Orro Hann. 
The disintegration theory of Rutherford and Soddy has brought forward 
a long list of radio-active products, which have distinct chemical and 
physical properties, and which may be separated by various methods, 
Some of these products emit @ particles, some 8 particles, some emit 
