1

Composition of Weldon Mud. {Capes News,
Now, when CaOMnO, is treated by a sufficient quantity
of MnCl, two successive reactions take place; the first,
which I will call A, being represented by the equation :—
2CaOMnO,+ MnCl; =Ca0(MnO,), + CaCl, + MnO ;
and the second, which I will call C, by the equation :—
Ca0(MnO,)z+ MnCl; = MnO(MnO;,), + CaCl,.
Reaction A takes place extremely readily, and is always
sompleted before reaction C begins. Indeed, if there be
any MgO present, aed if the MnCl, be added gradually,
1s it always is in pra&ice, after reaction A has been comsleted
 and before reaction C begins, what]I will call reaction
B takes place, this being simply the decomposition of
¥nCl; by MgO. As reactions A and B yield free MnO,
which can absorb oxygen, while rea&tion B moreover
affords a simple means of avoiding the serious loss and
‘convenience which would otherwise result from the ac.
:umulation in the mud of the MgO contained in the lime
ised, there is practical advantage in adding, as * final
iquor,” enough MnCl, to effe& reaions A and B, and
-hen continuing the inje@ion of air until the resulting
MnO has absorbed as much oxygen as it can; but there
would be no advantage in adding more than that quantity
of final MnCl,, because the MnO resulting from the rea&ion
 of MnCl, on CaO(MnOy,), simply replaces the CaQ
of that compound, converting it into MnO(MnO,),, the
MnO in which cannot be made to take up oxygen in the
vet way. In well-conduéted operations, therefore, no
more final MnCl, is used than will convert all CaOMnO,
nto CaO(MnOy),, and all MgO into MgCl,. Still it does
lappen sometimes, exceptionally and by accident, that
:nough final MnCl, is added to produce, not only reactions
A and B, but also rea&ion C, with the effe& of replacing
by MnO(MnO,), the Ca0(MnO,), which would otherwise
aave been contained in the final produc, and which is the
srincipal constituent of the final produ of operations
made in the ordinary way. It follows that the complete
absence of lime from finished Weldon mud would not,
of itself, in the least vitiate the theory that the results
obtained in the Weldon oxidiser are due to the intermeliate
 formation of calcium manganites, and that whatever
ime exists in finished mud which has been made with
* final liquor,” whether its quantity be great or small—
ind it may be very small indeed, even when rea®ion C
1as been entirely avoided, if the degree of oxidation of the
manganese is low, owing to too small an “excess” of
ime having been used—exists therein as CaO(MnO,),.
Chis is a very different theory from that which Dr. Post
ittributes to me, and it can neither be proved nor dissroved
 by even accurate determinations of the quantity of
a0 in the final produ&®. To bein a position to discuss
t at all, one must know the whole history of the produ,
and have observed qualitatively and quantitatively, all
-hat has taken place from beginning to end of the opera.
ion by which it was made. And yet I am privileged to
vead, in an “abstra®” in a recent number of the
*“ Journal ”” of the Chemical Society, that Dr. Post's estimation
 of the CaO in certain samples of finished mud,
* show the theories of Weldon . . . . to be inaccurate.”
if, however, finished Weldon mud may contain no lime
at all, and yet my theory as to the part which lime plays
n the oxidiser nor be inaccurate, why do I hold that the
samples analysed by Dr. Post really contained more lime
:han he found in them? Let me put the answer as
‘ollows :—According to the half million analyses, the
average proportion of “ base” in Weldon mud is about
2'7, that is to say, per equivalent of MnO, in it there is
usually seven-tenths, or nearly seven-tenths, of an equi.
valent of protoxides. This result of the half-million
analyses is confirmed by the manufacturing result that
or every kilogramme of chlorine liberated by means of
Weldon mud, the quantity of hydrochloric acid at 32 per
rent which is decomposed and neutralised by the mud,
wverages ten and a hall kilogrammes, less the quantity
afterwards neutralised by about 08 of a kilogramme of
CaCOs But Dr, Post’s analyses show very much less

CORRESPONDENCE.

COMPOSITION OF WELDON MUD.

To the Editor of the Chemical News.
S1R,—Dr. Post, in the CremicAL NEWS (vol. xli., p. 276),
attributes to me a formula, to satisfy which, he says,
would require that the 0°58 per cent of Mg, which he
Jound in a certain sample of Weldon mud, should be combined
 with 4°20 per cent, or zo equivalents of MnO;, and
would further require that the o-6o per cent of Fe,0,,
which he also found in that sample, should be combined
with 1-305 per cent of MnO,, or in the proportion of 40
of MnO; to 1-0 of Fe;03. Will you allow me to say that
I have never given any such formula. On the contrary,
while I have proved that MgO and MnO, can be made to
combine in the dry way, though not in the proportions
given by Dr. Post, but only in that of 10 of MnO, to 2'0
of MgO, I have also proved that MnO, does not combine
 with MgO at all in the wet way under the conditions
which obtain in the Weldon oxidiser, and under which
CaO, Sr0, Bao, Na;0, and K,0, a!l combine with MnQ,,
and that neither in the wet way nor in the dry way, under
any conditions yet realised, will MnO, combine either with
Fe;03 or any other sesquioxide whatever.
Alike in his communication to you, and in four papers
previously contributed to German journals, Dr. Post main-:ains
 that his determination of the quantity of CaO in certain
 samples of Weldon mud, prove that the explanations
which I have given of what takes place in the Weldon
process are incorre®., I reply that Dr. Post failed to find
in his samples all the lime really contained in them, and
that if his acquaintance with the chemistry of the Weldon
process were as complete as that of one who is endeavour.
ing to set us all right about it should be, he would know
that the theory that the results of that process are due to
the formation of compounds of MnO, with CaO is quite
compatible with the non-existence of any lime at all in
finished mud, made, as all Weldon mud is now-a-days,
with what is called * final liquor.”
Some fifty thousand samples of Weldon mud are now
analysed per annum. Since the process was first intro-1uced,
 more than half a million samples have been ana.
sysed. Dr. Post has analysed only three or four samples,
Che half million results are on one side, Dr. Post’s three
or four results are on the other, It does happen some-:imes
 that one man is right and all the rest of the world
wrong, But in this case there are circumstances which
make it immeasurably improbable that Dr. Post is right.
Weldon mud is made for the Furpose of obtaining, by
means of it, chlorine-produds for sale. Important
elements in the cost price of chlorine-produés are the
quantities «.f lime and limestone required to produce the
Weldon mud, and the quantity of acid required to dissolve
 it. These quantities are therefore recorded regularly
in every chlorine-work- in the world, and from them the
composition of the mud can be calculated, due note being
taken of any loss of free chlorine; and calculation from
‘hese data confirms the results of the half million analyses,
and utterly condemns Dr. Post's. If Dr. Post’s analyses
were accurate, to produce the quantity of chlorine now
manufactured per annum would require some 14,000 tons
iess lime, and some 70,000 tons less hydrochloric acid,
than we know that it actually does require,
In a paper replying to Dr. Posts first two German
papers on this subjects which I read before the Newcastle
Chemical Society on the 25th March last, and to which I
would beg to refer any of your readers who may care to
snquire into the evidence for the existence of manganites,
I have shown that the contents of the Weldon oxidiser,
vhen oxidation has ceased to advance, before the addition
 of the ‘final liquor,” consist partly of Mn,Oj, but
mainly of MnO, combined with CaO, partly as CaOMnO,,
or CaMnOj;, and rartly as CaO(MnO,),, or CaMn,O..