Solid Compounds of Sulphur Trioxide, Water, and the Bi-sulphates or Acid Sulphates of Sodium or Potassium.
Year: 1891

page_text: Date of Application, 17th Oct., 1891
Complete Specification Left. 15th Aug., 1892-Accepted, 17th Sept., 1892
PROVISIONAL SPECIFICATION.
New Solid Compounds of Sulphur Trioxide, Water, and the
Bi-sulphates or Acid Sulphates of Sodium or Potassium.
I, GEORGE FREDERICK BRINDLEY, of 47 Douglas Road, Handsworth, in
the County of Stafford, Chemist, do hereby declare the nature of this invention to
be as follows:-
The transport of free sulphuric acid or oil of vitriol, which is a liquid at ordinary
temperatures, to great distances, is attended with dangers and difficulties so great
as to be practically prohibitory; and to obviate those dangers and difficulties,
attempts have been made to combine the acid with sulphate of sodium in such
form as to produce a solid substance which may be readily transported at ordinary
temperatures. These attempts have hitherto been unsuccessful, because practically
only the bi-sulphates have been prepared, and this compound, although solid,.
contains too little excess sulphuric acid to be of much value. for the purposes for
which sulphuric acid is required in practical operations.
My invention consists in certain new compounds which I have discovered of a
solid nature and yet containing a relatively large proportion of sulphur trioxide SO,;
and also in the methods of preparing these new compounds. To make the nature
of these compounds readily understood it is necessary to state that sulphur
trioxide (SO) forms at least three hydrates or definite compounds with water;
these are 2 SOH₂O; SO₂H₂O; and SO, 2 H₂O; these compounds are sometimes
written as follows respectively H₂SO SO; H.SO; and H.SO HO; the inter-
mediate hydrate consisting of one equivalent of SO, and one of H,O being known
as sulphuric acid proper.
I have found that these three hydrates combine with the bi-sulphate of sodium
or potassium to form crystalline compounds which are solid at ordinary tempera-
tures, but are decomposed on the addition of water into sulphuric acid and the
sulphate of the alkali.
Three definite compounds are produced :-
:-
(a) 2 SO,H,O, RHSO, (6) SO,H,O, RHSO (c) SO, 2 H₂O, RHSO̟.
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In these formulæ, R represents potassium or sodium. I have also obtained bodies
of intermediate composition by combining the compounds under (a) (b) and (c) as
follow (d) 3 SO, 3 H,O, 2 RHSO, from (a) and (c). (e) 2 SO, 3 H,O, 2 RHSO.
from (b) and (c).
J
The object, it will clearly understood is to obtain a compound with a maximum
of sulphur trioxide (SO) in a solid state suitable for safe transport, and these new
bodies either singly or in combination or mixtures, supply suitably stable solid
compounds for the purpose I have in view.
I prepare the above mentioned compounds in the following manner: I take or
prepare any of the above mentioned hydrates and I add thereto the requisite
weight of bi-sulphate of sodium or potassium to form the required compound.
heat the mixture gently until the salt has dissolved, and allow the solution to cool
when it crystallizes or sets into a solid mass. Or I may take mixtures of these
hydrates, with water, and either before or after the addition of the sodium or
potassium salt, drive off the excess of water by heat and then allow to cool and
crystallize.,
I may also take normal sulphates of sodium or potassium (Na,SO, or K,SO,)
and add sufficient sulphuric acid to form the required bi-sulphate; likewise the
sulphates of sodium or potassium obtained as bye products in the manufacture of
hydro-chloric acid and nitric acid may be used or pyro or anhydrous bi-sulphates
of sodium or potassium.

page_text: sulphuric acid as contains 196 parts of H₂SO, and slowly evaporating by heat
till the temperature rises to, but does not exceed 260° centigrade.
The analysis of the pure sodium compound which may be so obtained is:-
Na,SO 31.27%; SO, = 52.86%, and water 15.87% while the pure potassium
compound is-K₂SO₁ = 35.8%; SO, = 49.38% and water 14-820
=
8
10°
The sample of the commercial sodium compound so produced has the analysis:
Ná₂SO 32:22%; SO, 54.15%; water 13.63%, while the sample of the
commercial potassium compound has the composition:-K,SO=36-4°
49-97% and water 13.63%
=
SO
In preparing these compounds on the manufacturing scale allowance must be
made for the impurities in the materials employed and the inaccuracy in the hydro-
meters used to obtain the specific gravity of the acid and likewise any errors in the
thermometers used for determining the temperatures at which concentration by
evaporation must cease in order to produce the various compounds. To allow of
such inaccuracies I find it advisable to employ from 2 to 3% excess of the base
salt from the proportions herein.before given.
1.
When the strongest commercial sulphuric acid is employed in manufacturing the
above compounds it is advisable to first convert the alkaline sulphate used into
bi-sulphate in any well known manner.
When dilute acid is used it is better to convert the sulphate first into bi-sulphate
also.
By the methods herein before described using the mixtures in the proportions
given and evaporating to the temperatures noted solid compounds are obtained
containing large proportions of H.SO, and capable of easy and safe storage and
transport.
1
.. ...
The solution of the salts in the herein before mentioned hydrates of sulphur
trioxide to form the compounds respectively indicated, may he conveniently
effected in iron vessels, provided the specific gravity of the mixture before the
addition of the salt bé not lower than 1.65.
t-f
74 f
When the desired compound has been obtained the hot liquid may be run into
iron drums, or other vessels in which it may be allowed to cool and crystallize' or
set solid, or it may be poured into broad shallow vessels and allowed to cool 'and
solidify after which it may be broken up to be stored and packed.
I find in practice that it is advisable to run the hot liquid into drums and touch
the liquid with a crystal of the compound or throw in a crystal or stir à little as
the liquids have the property of supersaturation in a high degree and remain
liquid when allowed to stand for a longer time than occurs when solidification is
induced by stirring or by a crystal.
I find that by conducting the latter part of the evaporation in a pan with a
cover having an opening from 3 to 6 inches diameter I am enabled to push the
evaporation rapidly without loss of acid.
:
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what 'I
claim is:-
The hereinbefore described new compounds and the process of manufacturing
solid compounds of the bi-sulphates of sodium and potassium having the chemical
formule given below by mixing the respective salts with sulphuric acid in a heated
state and
and evaporating if the acid used be too weak till the temperatures of the
fused compound rises to the temperatures appended to each compound. "The
compounds prepared and the maximum temperatures of evaporation are as
follows
.al.

page_text: MARKS & CLERK,
13, Temple Street, Birmingham, Agents for Applicant.