An Improved Method of Obtaining Metallic Sodium.
Year: 1890

page_text: Date of Application, 9th Oct., 1890-Accepted, 29th Nov., 1890
AUMIT LEIE DIMIFICATION.
An Improved Method of Obtaining Metallic Sodium.
1. LUDWIG GRABAU, of Hanover, in the Empire of Germany, Civil Engineer, do
hereby declare the nature of this invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
This invention relates to the electrolytic production of metallic sodium from sodium
chloride.
The methods heretofore tried and proposed of obtaining metallic sodium by electro-
lysing fused culinary salt have not met with success, extremely little or no metallic
sodium being thereby separated from the culinary salt or sodium chlorido fusing
at a bright cherry red as the nascent sodium immediately combines with the
excess of culinary salt so as to form sodium subchloride which has been made known
by H. Rose and Bunsen, this subchloride being distributed in the molten mass and
partly oxidized on the surface of the latter and partly retransformed into sodium
chloride by the chlorine which is freed at the positive pole.
According to the present invention based on extensive experiments effectually
provide against this behaviour of the metallic sodium by lowering the temperature of
fusion of the bath of culinary salt or sodium chloride which is obtained by adding to
the said culinary salt or sodium chloride on the one hand potassium chloride and on the
other hand calcium chloride or strontium chloride or barium chloride or a mixture of
the same.
The alkaline chlorides are used with good results in the proportion of equal
molecules, and of the earthy alkaline chloride it is expedient to employ 1 molecule for
3 molecules of the mixed alkaline chlorides. Such a tri-salt mixture fuses very rapidly
namely below dark red. The experiments made here show that strontium chloride is
preferable to the other two earthy alkaline chlorides inasmuch as barium chloride gives
a mixture which is somewhat less fusible whilst calcium chloride can with difficulty be
freed from the water.
Now whilst from pure fused culinary salt or sodium chloride scarcely any sodium is
obtained by electrolysis owing to the secondary formation of subchloride caused by the
high temperature of fusion, the electrolysis of the tri-salt mixture, provided the
temperature is not raised above the degree necessary for the fusion, gives about
95 per cent. of the quantity of metal determined according to Faraday's law.
If the potassium chloride is kept from the bath the mixture becomes considerably
more difficult of fusion and the yield is lowered from 95 per cent. to less than
50 per cent.
Despite the comparatively small quantity of culinary salt or sodium chloride in the
tri-salt mixture the metal separated is almost pure sodium it does not contain any trace
of earthy alkaline metal and only about three per cent. of potassium which amount does
not preclude its use for industrial and other important purposes. If desired the
potassium can be removed by an oxidizing remelting operation.
As according to the extent of the metal separated the composition of the bath can be
easily maintained uniform by the addition of culinary salt or sodium chloride and a
small quantity of potassium chloride corresponding to the average quantity of
potassium contained in the nascent sodium my improved method enables the industrial
production of sodium from fused culinary salt or sodium chloride by electrolysis.
It will be readily observed that by reason of the great fusibility of the tri-salt
mixture the technical difficulties in respect of the durability and strength of the
melting vessels and carbon electrodes and as regards the convenience of operation are
considerably diminished.

page_text: 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 preparation of metallic sodium from culinary salt or sodium chloride by
electrolysis by the fire-liquid method by adding to the culinary salt or sodium chloride
to be electrolysed on the one hand potassium chloride, and on the other hand calcium
chloride, strontium chloride or barium chloride or a mixture of two or three of these
earthy alkaline chlorides.
Dated this Oth day of October 1890
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.