Rosco Bodine
February 4th, 2004, 05:46 PM
Having obtained the full texts for two old British patents related to
a simplified method for producing azides , I am sharing this
obscure and interesting information with others who may wish
to experiment with and elaborate upon this process .
GB128014 , Complete Specification ,
Improvements in and relating to the Production of Azides
application date: June 17 , 1918 No. 9952 / 18
complete accepted : June 17 , 1919
I , William Richard Hodgkinson , C.B.E. , of Ordnance College ,
Woolwich , London , S.E. 18 , Professor of Chemistry and Metallurgy ,
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 production of azides .
The object of the invention is to provide a process of producing
azides from salts of hydrazine without the employment of
ethyl benzoate or the like , and the formation of benzoyl hydrazine .
According to the invention , salts of hydrazine are diazotised
by means of a suitable nitrite under such conditions that the
reaction mass is at no time so distinctly acid as to redden
litmus paper , but appears on the border line of acidity and alkalinity .
The conditions of acidity under which the reaction is carried out
according to the invention , are preferably comparable with the
conditions of acidity as indicated by litmus paper , of ,
for instance a solution of boric acid . Thus in accordance with
the invention , the nitrite solution is brought together with a
salt of hydrazine in approximately the proportions required on the
basis of theory to diazotise the hydrazine , under such conditions
that the acidity never exceeds the degree of acidity indicated above ,
and an acidified salt of the metal of which the azide is required ,
is introduced into the mixture , or alternatively the mixture
is added to the solution of the salt of the metal .
For example , silver azide is formed by adding a neutral solution
of hydrazine sulphate and sodium nitrite in molecular proportions
to a solution of silver nitrate of a degree of acidity with nitric acid
enabling the conditions in regard to acidity set forth above to
be realised , while avoiding the precipitation of silver sulphate .
Thus , for example 130 grams of hydrazine sulphate is converted
to the neutral hydrazine ammonium sulphate , which is more soluble
in water than is the simple hydrazine sulphate , by the addition of
ammonia solution , the mixture being made up to about 500 ccs .
To this solution contained in a vessel in which it can be violently
agitated , the calculated amount of sodium nitrite dissolved in
500 ccs. of water is added slowly so that the temperature does not
rise much above 30 degrees Centigrade .
The reaction resulting in the formation of sodium azide may be
represented by the following equation :
N2H4-H-NH3-H-SO4 + NaNO2 ------> NH4HSO4 + NaN3 + 2 H2O
From this equation it will be seen that the solution would become acid
as the result of the reaction were it not for the fact that sodium nitrite
is never pure but is alkaline , the alkali in the nitrite ordinarily
being sufficient to maintain the solution on the border line of
acidity and alkalinity , and addition of a small quantity of alkali
being made should such not be the case . The solution thus made
contains sodium azide , some unchanged reagents , and the
by-products of the reaction .
The sodium sulphate and sodium azide contained in the solution
may be separated by crystallisation but preferably the solution
is added gradually to an acidified solution of silver nitrate produced
by adding 1. 0 cc. of 70% of nitric acid to 1000 ccs. of a
normal solution of silver nitrate which is violently agitated
during such adding , the temperature of the reaction mass being
prevented from rising much higher than 30 - 40 degrees Centigrade .
With adequate cooling and agitation the yield of silver azide may
be obtained equivalent to 85 % of the calculated possible amount .
Instead of adding the diazotised solution to the acidifed silver nitrate
solution , the latter may be added to the former .
When starting from hydrazine nitrate which is also an acid salt ,
a solution of ammonia should be added in order to form the
neutral hydrazine ammonium salt or , if desired , the neutral
hydrazine sodium salt may be produced , the remaining steps
of the process being then carried out as above described .
In producing lead azide , a solution of a hydrazine salt
of an acid which will not result in the precipitation of
an insoluble lead salt of the acid in question , for instance
hydrazine nitrate , is employed , and the reaction mass
in this case should be only just acid , as lead azide is
particularly easily acted on by acids , while in producing
silver azide the acidity of the reaction mass may be greater
in order to avoid the precipitation of silver sulphate
and agitation indicated in the foregoing example .
The azides produced in accordance with the invention
are usually amorphous , and in this state they are
safer to handle than when crystalline .
Having now particularly described and ascertained the nature
of my said invention and in what manner the same is to be
performed , I declare that what I claim is :
1. The process of producing azides from salts of hydrazine
in which salts of hydrazine are diazotised by means of
a suitable nitrite under such conditions that the reaction mass
is at no time so distinctly acid as to redden litmus paper ,
but appears on the border line of acidity and alkalinity .
2. The process as claimed in Claim 1 in which the conditions
of acidity under which the reaction is carried out according
to the invention are preferably comparable with conditions
of acidity as indicated by litmus paper , of , for instance ,
a solution of boric acid .
3. The process of producing azides from salts of hydrazine ,
substantially as hereinbefore described .
Dated this 10th day of December , 1918
Regarding the second patent GB129152 ,
It simply states that another method of isolating
sodium azide is to agitate in cool water a suspension
of silver azide with slightly less than the theoretical amount
of sodium chloride for a few minutes , and filter the precipitated
silver chloride . The residual solution of sodium azide is
evaporated on a steam bath to yield a concentrated solution
of sodium azide . The reaction proceeds according to the equation
AgN3 + NaCl -----> AgCl + NaN3
The sodium azide produced may be used in double decomposition
reactions to form whatever other azides are desired .
a simplified method for producing azides , I am sharing this
obscure and interesting information with others who may wish
to experiment with and elaborate upon this process .
GB128014 , Complete Specification ,
Improvements in and relating to the Production of Azides
application date: June 17 , 1918 No. 9952 / 18
complete accepted : June 17 , 1919
I , William Richard Hodgkinson , C.B.E. , of Ordnance College ,
Woolwich , London , S.E. 18 , Professor of Chemistry and Metallurgy ,
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 production of azides .
The object of the invention is to provide a process of producing
azides from salts of hydrazine without the employment of
ethyl benzoate or the like , and the formation of benzoyl hydrazine .
According to the invention , salts of hydrazine are diazotised
by means of a suitable nitrite under such conditions that the
reaction mass is at no time so distinctly acid as to redden
litmus paper , but appears on the border line of acidity and alkalinity .
The conditions of acidity under which the reaction is carried out
according to the invention , are preferably comparable with the
conditions of acidity as indicated by litmus paper , of ,
for instance a solution of boric acid . Thus in accordance with
the invention , the nitrite solution is brought together with a
salt of hydrazine in approximately the proportions required on the
basis of theory to diazotise the hydrazine , under such conditions
that the acidity never exceeds the degree of acidity indicated above ,
and an acidified salt of the metal of which the azide is required ,
is introduced into the mixture , or alternatively the mixture
is added to the solution of the salt of the metal .
For example , silver azide is formed by adding a neutral solution
of hydrazine sulphate and sodium nitrite in molecular proportions
to a solution of silver nitrate of a degree of acidity with nitric acid
enabling the conditions in regard to acidity set forth above to
be realised , while avoiding the precipitation of silver sulphate .
Thus , for example 130 grams of hydrazine sulphate is converted
to the neutral hydrazine ammonium sulphate , which is more soluble
in water than is the simple hydrazine sulphate , by the addition of
ammonia solution , the mixture being made up to about 500 ccs .
To this solution contained in a vessel in which it can be violently
agitated , the calculated amount of sodium nitrite dissolved in
500 ccs. of water is added slowly so that the temperature does not
rise much above 30 degrees Centigrade .
The reaction resulting in the formation of sodium azide may be
represented by the following equation :
N2H4-H-NH3-H-SO4 + NaNO2 ------> NH4HSO4 + NaN3 + 2 H2O
From this equation it will be seen that the solution would become acid
as the result of the reaction were it not for the fact that sodium nitrite
is never pure but is alkaline , the alkali in the nitrite ordinarily
being sufficient to maintain the solution on the border line of
acidity and alkalinity , and addition of a small quantity of alkali
being made should such not be the case . The solution thus made
contains sodium azide , some unchanged reagents , and the
by-products of the reaction .
The sodium sulphate and sodium azide contained in the solution
may be separated by crystallisation but preferably the solution
is added gradually to an acidified solution of silver nitrate produced
by adding 1. 0 cc. of 70% of nitric acid to 1000 ccs. of a
normal solution of silver nitrate which is violently agitated
during such adding , the temperature of the reaction mass being
prevented from rising much higher than 30 - 40 degrees Centigrade .
With adequate cooling and agitation the yield of silver azide may
be obtained equivalent to 85 % of the calculated possible amount .
Instead of adding the diazotised solution to the acidifed silver nitrate
solution , the latter may be added to the former .
When starting from hydrazine nitrate which is also an acid salt ,
a solution of ammonia should be added in order to form the
neutral hydrazine ammonium salt or , if desired , the neutral
hydrazine sodium salt may be produced , the remaining steps
of the process being then carried out as above described .
In producing lead azide , a solution of a hydrazine salt
of an acid which will not result in the precipitation of
an insoluble lead salt of the acid in question , for instance
hydrazine nitrate , is employed , and the reaction mass
in this case should be only just acid , as lead azide is
particularly easily acted on by acids , while in producing
silver azide the acidity of the reaction mass may be greater
in order to avoid the precipitation of silver sulphate
and agitation indicated in the foregoing example .
The azides produced in accordance with the invention
are usually amorphous , and in this state they are
safer to handle than when crystalline .
Having now particularly described and ascertained the nature
of my said invention and in what manner the same is to be
performed , I declare that what I claim is :
1. The process of producing azides from salts of hydrazine
in which salts of hydrazine are diazotised by means of
a suitable nitrite under such conditions that the reaction mass
is at no time so distinctly acid as to redden litmus paper ,
but appears on the border line of acidity and alkalinity .
2. The process as claimed in Claim 1 in which the conditions
of acidity under which the reaction is carried out according
to the invention are preferably comparable with conditions
of acidity as indicated by litmus paper , of , for instance ,
a solution of boric acid .
3. The process of producing azides from salts of hydrazine ,
substantially as hereinbefore described .
Dated this 10th day of December , 1918
Regarding the second patent GB129152 ,
It simply states that another method of isolating
sodium azide is to agitate in cool water a suspension
of silver azide with slightly less than the theoretical amount
of sodium chloride for a few minutes , and filter the precipitated
silver chloride . The residual solution of sodium azide is
evaporated on a steam bath to yield a concentrated solution
of sodium azide . The reaction proceeds according to the equation
AgN3 + NaCl -----> AgCl + NaN3
The sodium azide produced may be used in double decomposition
reactions to form whatever other azides are desired .