494 
PHOSPHATE AND PYROPHOSPHATE OF SODA. 
diversity of colour from varnished card 
of several colours, when viewed under 
certain circumstances, through eye- 
pieces of tourmaline, Iceland spar, &c, 
(we omit the detailof these experiments, 
as every one of them have been shown to 
he consequences of the undulatory the- 
ory of light) ; 3. By transmitting the 
ray through certain crystalline sub- 
stances, such as Iceland spar ; 4. By 
passing the ray through crystals of tour- 
maline cut by planes parallel to the axis 
of the crystal ; 5. By the use of Nicholls 
double fosion of Iceland spar, of the 
action of which upon light, the rev, gen- 
tleman took, as it appeared to us, an 
entirely erroneous view, for he stated 
that the. rays which had been separated 
within these prisms, were reunited upon 
their emergence, whereas the very nature 
of the prism is to prevent that reunion, 
by causing a total reflection of the ordi- 
nary ray at the oblique common surface 
of the two prisms, (between which, the 
Canada balsam is interposed). The rev. 
gentleman then proceeded to explain, in 
connexion with his theoretic views, the 
play of colours observed within certain 
kinds of crystals of Iceland spar, the dis- 
tinction between right-handed and left- 
handed quartz crystals, and numerous 
other instances derived from facts fami- 
liar to those who have studied this 
branch of science. 
Section B.~CHEMISTRY AND 
MINERALOGY. 
President - Rev Professor Cdmming. 
Vice P residents ••'Dr . Dalton, Dr Henry 
Secietaries-'^Yir Apjohn, Dr. C Henry, W. 
Herapath, Esq 
Committee --Tir Barker, Professor Daubeny, 
Charles T Coathupe, Esq., Rev. W Vernon 
Harcourt, Professor Hare. Professor John- 
ston, Georg:e Lowe, Esq , F R. S. Professor 
Miller, Riclnrtl Phillii)s, Esq , Dr. Roget, 
Dr Ro' er, D Thomson Dr. Turner, Dr. T 
Thomson, T. Thompson jun.,Esq., Henry 
Hou^hWatson, Esq., Wil iam West, Rev. 
Wil iam Whewell, Dr. Tellowly, Colonel 
Yorke, 
Mr, Watson read a paper on the Phos- 
phate and Pyrophosphate of Soda; — 
one, however, of so much detail, as 
scarcely to admit of compression. The 
results at which he arrived are the fol- 
lowing : — 1st, That Phosphoric acid 
given off water in being converted into 
the pyropbosphoric acid, and that hy- 
drogen and carbon are component parts 
of the former. 2nd, That phosphoric 
and Pyrophosphoric acids are alto- 
gether different, — different in their i 
composition and their atomic weight ; | 
that of the phosphoric being 36T, 
and that of pyrophosphoric, acid, ' 
31.7. 3rd, That the precipitate given by 
pyrophosphate of soda and lime water, 
when calcined, is black ; that afforded by 
phosphate of soda and lime water white. 
4th, That, contrary to the prevailing 
opinion, a solution of the pyrophosphate 
of soda does not spontaneously change 
into phosphate. [The statement con- 
tained in this paper appeared to us ra- 
ther startling, and, we must add, in- 
conclusive.] 
Mr. Ettrick on a new form of Blow- 
pipe. — The principal novelty in this 
apparatus was the method employed for 
maintaining a constant blast indepen- 
dent <ff hydrostatic pressure. This was 
accomplished by small bellows, thrown i 
into very rapid action by means of a ! 
wheel and pinion, and a stop-cock in- 
serted in the tube connecting the bellows 
and cylindric reservoir. To prevent the 
air from being too much compressed, j 
the bellows were furnished with a valve, i 
opening outwards, and which was i 
pressed upon by a spring, the force of j 
which admitted of being very readily j 
varried. From the cylinder there are |j 
two eduction pipes, terminated by noz- || 
zles, so that by using these, and a pair 
of lamps, two jets of flame might be 
brought to bear 'upon the same object. 
He also explained, how air might be 
made to issue from one, and coal, or 
other inflammable gas, from the other ; 
and exhibited a tube similar to that long 
since described by professor Daniell, by 
the use of which a combustible atmos- 
phere might be made to issue from an 
orifice without any previous mixture in 
a reservoir. 
Dr. Hare, in observing on this paper, 
incidentally described the apparatus, 
which hehas for many years been in the 
habit of using, with a view to the fusion 
of refractory substances ; and stated, 
that the double tube of Daniell had been 
used by him many years before it was 
described by the person whose name it 
usually hears. Dr. Hare stated, that he 
had also used the double jet, but had 
long since laid it aside, from a convic- 
tion of its inutility. 
Mr. Herapath then drew the atten 
tion of the Section to the composition of 
Bath Water, as recently determined by 
