Vapor phase catalytic hydrolysis of benzal chloride or its halogen- or trifluoromethyl-substitute to form benzaldehyde or substitute

Vapor phase contact reaction between water and benzal chloride or a substitute expressed by C.sub.6 H.sub.(5-n) X.sub.n CHCl.sub.2, wherein X representing a halogen atom or a trifluoromethyl group and n being 1 or 2, to form benzaldehyde or a substitute expressed by C.sub.6 H.sub.(5-n) X.sub.n CHO can efficiently be achieved by using activated carbon treated with an acid such as sulfuric acid or impregnated with a metal chloride such as ferric chloride and/or a metal sulfate such as cupric sulfate as catalyst. The activated carbon catalyst long retains its high activity even when the starting material has trifluoromethyl group, which is liable to undergo partial decomposition with formation of hydrogen fluoride.

BACKGROUND OF THE INVENTION 
This invention relates to a process of preparing benzaldehyde or a 
substitute expressed by C.sub.6 H.sub.(5-n) X.sub.n CHO, wherein X 
represents a halogen atom or trifluoromethyl group and n is 1 or 2, by 
vapor phase catalytic reaction between water and benzal chloride or a 
substitute expressed by C.sub.6 H.sub.(5-n) X.sub.n CHCl.sub.2. 
Benzaldehyde and its substitutes of the above defined class are 
industrially of use as materials for the synthesis of various organic 
compounds including some medicines and agricultural chemicals. It is 
possible to obtain benzaldehyde or its substitute of the above defined 
class by hydrolysis of benzal chloride or its substitute of the above 
defined class, but it is impracticable to achieve the hydrolysis by merely 
heating a mixture of benzal chloride or its substitute with water because 
the hydrolysis proceeds only at a very low rate. 
Accordingly various catalysts have been proposed for liquid phase 
hydrolysis of benzal chloride or its substitute to form benzaldehyde or 
its substitute. Typical examples of the hitherto proposed catalysts are as 
follows: (1) aqueous solution of acid or alkali; (2) cuprous chloride or 
cupric chloride; (3) aqueous solution of iron salt; (4) anhydrous zinc 
chloride; and (5) zinc oxide. 
However, every process using one of these catalysts is disadvantageous in 
certain respects from an industrial point of view. More particularly, the 
use of an aqueous solution of an acid or an alkali (1) is liable to cause 
undesirable side reactions and, besides, is almost ineffective for the 
hydrolysis of substituted benzal chlorides having an electron attractive 
group typified by trifluoromethyl group. Furthermore, if this process is 
put into industrial practice it becomes a requisite to the process to use 
a reaction vessel of very large capacity relative to the quantity of the 
compound subjected to hydrolysis, and the waste acid or alkali must be 
treated with considerable trouble. Any one of the processes using the 
metal salt catalysts (2), (3) and (4) suffers from an unsatisfactorily low 
rate of reaction, and this problem becomes very serious when the starting 
material is a substituted benzal chloride having an electron attractive 
group, and an increase in the quantity of the metal salt catalyst with a 
view to enhancing the reaction rate significantly promotes unfavorable 
side-reactions. The use of zinc oxide catalyst (5) is almost ineffective 
for hydrolysis of a trifluoromethyl-substituted benzal chloride and, 
besides, is unsuitable to a continuous process because of the need for the 
step of separating zinc oxide from the reaction product. 
Due to such problems or disadvantages, none of the hitherto proposed liquid 
phase catalytic hydrolysis processes can be taken as suitable to 
industrial practice. 
Japanese Patent Application Primary Publication No. 48(1973)-5733 proposes 
a vapor phase catalytic reaction process for the hydrolysis of benzal 
chloride or its substitute characterized by using silica or alumina as 
catalyst either in pure state or in a state impregnated with cuprous 
chloride or cupric chloride. This process can be performed as a continuous 
process since the reaction takes place in vapor phase, but this process 
has the following shortcomings. In the case of using either silica or 
alumina in pure form as the catalyst, it is practically impossible to 
achieve the intended hydrolysis of a trifluoromethyl-substituted benzal 
chloride firstly because the rate of the reaction is very low even at an 
initial stage where the catalyst is in a fresh state, and secondly because 
the catalyst is easily fluorinated by hydrogen fluoride formed by 
hydrolysis of a portion of the trifluoromethyl group of the starting 
material and, therefore, is rapidly deactivated. Even in the case of using 
a silica or alumina catalyst impregnated with cuprous chloride or cupric 
chloride, the activity of the catalyst is insufficient for efficient 
hydrolysis of a trifluoromethyl-substituted benzal chloride and rapidly 
and significantly lowers with the lapse of time, so that the hydrolysis 
can hardly be performed as a truly continuous process. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a vapor phase catalytic 
hydrolysis process for the preparation of benzaldehyde or its halogen- or 
trifluoromethyl-substitute from benzal chloride or its halogen- or 
trifluoromethyl-substitute, which process is readily practicable as a 
continuous process and in which process the hydrolysis proceeds very 
rapidly without suffering from significant deactivation of the catalyst 
even when the starting material is a trifluoromethyl-substituted benzal 
chloride, so that the intended product is obtained with high purity and 
high yield. 
A process according to the invention is for the preparation of a compound 
expressed by the general formula (I) and has the step of carrying out a 
vapor phase contact reaction between water and a compound expressed by the 
general formula (II) at an elevated temperature in the presence of a 
catalyst: 
##STR1## 
in both the formulas (I) and (II) X representing a halogen atom or a 
trifluoromethyl group, and n being 0, 1 or 2. As the improvement according 
to the invention, the catalyst comprises activated carbon as a fundamental 
components thereof. 
More specifically, the catalyst in a process according to the invention is 
activated carbon treated with an acid, preferably with sulfuric acid, or 
activated carbon impregnated with a metal chloride typified by ferric 
chloride and/or a metal sulfate typified by cupric sulfate. 
An activated carbon catalyst used in the present invention exhibits very 
high activity on the vapor phase hydrolysis of benzal chloride or its 
substitute of the above defined class even when the substitute has a 
strongly electron-attractive group typified by trifluoromethyl group and 
is high in boiling point and rather difficult to hydrolyze. Accordingly 
the intended hydrolysis reaction proceeds very rapidly, and therefore the 
hydrolysis operation can be performed rapidly in a reaction vessel of 
relatively small capacity. Furthermore, the activated carbon catalyst is 
scarcely influenced by hydrogen fluoride, which is formed by hydrolysis of 
a portion of the trifluoromethyl group in the starting material, and 
retains its high activity for a long period of time. Therefore, a high 
rate of conversion of benzal chloride or a substituted benzal chloride to 
the intended compound (I) can be attained irrespective of the kind of the 
starting compound (II). Because of these features, the invention is fully 
practicable as a continuous and industrial process with many advantages 
over the hitherto proposed processes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Besides benzal chloride, the following compounds can be named as typical 
examples of substituted benzal chlorides useful in the process according 
to the invention: o-, m- or p-chlorobenzal chloride, o-, m- or 
p-bromobenzal chloride, o-, m- or p-fluorobenzal chloride, o-, m- or 
p-trifluoromethylbenzal chloride, 2,4-dichlorobenzal chloride, 
2,5-dichlorobenzal chloride, 2,6-dichlorobenzal chloride, 
2,4-dibromobenzal chloride, 2,5-dibromobenzal chloride and 
2,6-dibromobenzal chloride. 
By the process according to the invention benzal chloride and the 
above-named substituted benzal chlorides are hydrolyzed to the following 
compounds, respectively: benzaldehyde, o-, m- or p-chlorobenzaldehyde, o-, 
m- or p-bromobenzaldehyde, o-, m- or p-fluorobenzaldehyde, o-, m- or 
p-trifluoromethyl benzaldehyde, 2,4-dichlorobenzaldehyde, 
2,5-dichlorobenzaldehyde, 2,6-dichlorobenzaldehyde, 
2,4-dibromobenzaldehyde, 2,5-dibromobenzaldehyde and 
2,6-dibromobenzaldehyde. 
As to activated carbon for use in the process according to the invention, 
no particular restrictions are placed on its type, particle shape or 
particle size, and therefore it suffices for the purpose of the invention 
to use a commonly used and commercially available activated carbon. 
In the case of treating activated carbon for use in the present invention 
with an acid, it is preferred to use sulfuric acid, hydrofluoric acid or 
phosphoric acid. In the state adsorbed and carried by activated carbon, 
any one of these acids exhibits a high catalytic activity on vapor phase 
hydrolysis of benzal chloride or a substituted benzal chloride. Since the 
vapor phase reaction in the method according to the invention is carried 
out at temperatures around 200.degree. C. though the reaction temperature 
is varied depending on the kind of the compound used as the starting 
material, it is most preferable to choose an acid the boiling point of 
which is above the intended reaction temperature. Sulfuric acid is a 
typical example of acids which meet this requirement. Besides, sulfuric 
acid is a readily available industrial material relatively low in price 
and relatively easy to handle. Therefore, sulfuric acid is the most 
preferred acid for treatment of activated carbon in the present invention. 
An activated carbon catalyst prepared by treatment with a preferred acid 
exhibits a very high catalytic activity in the hydrolyzing reaction in the 
process of the invention. In the presence of this catalyst, a contact 
reaction between steam and vaporized benzal chloride or a substituted 
benzal chloride proceeds very rapidly even when the starting compound has 
a strongly electron-attractive group typified by trifluoromethyl group, 
and it is possible to carry out the reaction as a continuous process. 
Furthermore, the activity of this catalyst hardly lowers even when 
hydrogen fluoride is formed in the reaction system by hydrolysis of a 
portion of the trifluoromethyl group of the starting compound, and 
therefore this catalyst retains its very high activity for a very long 
period of time. 
The acid treatment of activated carbon can be performed under various 
conditions insofar as the surface regions of the activated carbon 
particles can sufficiently be impregnated with the acid. From the 
viewpoint of surface activity, it is suitable to employ a relatively high 
acid concentration. In the case of treatment with sulfuric acid for 
example, it is suitable to use 95% (by weight) or more concentrated 
sulfuric acid. Both the temperature of the sulfuric acid solution and the 
immersion time to achieve the acid treatment of activated carbon can 
freely be determined. A practical range of the temperature is from room 
temperature to the boiling point of the employed sulfuric acid solution, 
and an immersion time of a few hours suffices for the purpose. For 
convenience of handling, the activated carbon after the acid treatment is 
washed with water and then dried at about 80.degree.-100.degree. C. 
In the case of using an activated carbon catalyst impregnated with a metal 
chloride and/or a metal sulfate, it is preferred to make a selection from 
the following compounds: manganese dichloride, ferric chloride, cobalt 
dichloride, nickel dichloride, palladium dichloride, cupric chloride, zinc 
chloride, tin dichloride, ferrous sulfate and cupric sulfate. In the state 
adsorbed and carried by activated carbon, any one of these metal salts 
exhibits a very high catalytic activity on vapor phase hydrolysis of 
benzal chloride and substituted benzal chlorides including those which 
have a strongly electron-attractive group typified by trifluoromethyl 
group and are high in boiling point and rather difficult to hydrolyze. 
Furthermore, an activated carbon catalyst of this type exhibits only a 
very small extent of lowering in its activity with the lapse of time and 
long retains its activity even when used in a reaction system in which 
hydrogen fluoride is formed by a side-reaction. 
As to the method of impregnating activated carbon with a metal chloride 
and/or a metal sulfate, a free choice can be made from known impregnating 
methods. However, usually it is convenient and suitable to employ an 
immersion method in which the activated carbon for treatment is kept 
immersed in an aqueous solution of a selected metal salt for a period of 
time ranging from a few hours to one day, followed by air-drying at about 
80.degree.-100.degree. C. The temperature of the solution during the 
immersion is not specified, and usually it suffices to leave the solution 
at room temperature. When it is intended to impregnate activated carbon 
with a relatively large amount of a metal sulfate which is generally low 
in solubility in water, it is suitable to perform the immersion treatment 
by adequately heating the sulfate solution. 
It is preferred that the total amount of the metal chloride and/or metal 
sulfate carried by activated carbon is in the range from 10 to 40% by 
weight of the activated carbon, firstly because the catalytic activity of 
the activated carbon impregnated with the metal salt is not always 
sufficiently high when the total amount of the metal salt is less than 10% 
by weight of the activated carbon and secondly because an increase in the 
amount of the metal salt beyond 40% by weight hardly results in a 
corresponding enhancement of the catalytic activity. The concentration of 
the metal salt solution may suitably be determined based on the desired 
amount of the metal salt to be carried by the activated carbon. 
The process according to the invention can be performed as a continuous 
process generally in the following way. 
As the first step, water and benzal chloride or a substituted benzal 
chloride are introduced into a heated vaporizer respectively at 
predetermined flow rates by using metering pumps to thereby vaporize the 
both materials. The temperature in the vaporizer should be above the 
boiling point of the compound to be hydrolyzed, and is determined such 
that a complete vapor phase may be maintained during the subsequent 
catalytic hydrolysis step with consideration of the feed rates of the 
materials relative to the capacity of the vaporizer. Another matter for 
consideration in determining the vaporizing temperature is to avoid 
significant evaporation of the acid or sublimation of the metal salt 
contained in the activated carbon catalyst during contact of the heated 
mixed gas with the catalyst. In general, a suitable range of the 
vaporizing temperature is from about 200.degree. C. to about 340.degree. 
C. 
The mixed gas prepared in the vaporizer is passed through a column packed 
with a selected activated carbon catalyst, which is kept heated at a 
temperature sufficient to maintain the supplied reactants in vapor phase 
but not so high as will cause significant evaporation of the acid or 
sublimation of the metal salt contained in the catalyst. In general the 
catalyst column is maintained at a temperature in the range from about 
150.degree. to 200.degree. C. in the case of using an activated carbon 
catalyst treated with acid, and in the range from about 100.degree. to 
300.degree. C. in the case of an activated carbon catalyst impregnated 
with a metal chloride or a metal sulfate. During contact with the packed 
catalyst, benzal chloride or the substituted benzal chloride contained in 
the mixed gas is hydrolyzed by reaction with steam in the mixed gas. 
As to the mole ratio of steam to the vaporized benzal chloride or 
substituted benzal chloride in this continuous process, it is suitable to 
use about one mole of water (steam) per each --CHCl.sub.2 group in the 
compound to be hydrolyzed from a stoichiometric viewpoint. In practice, 
however, it is suitable to use 5 to 10 moles of water (steam) per each 
--CHCl.sub.2 group. A preferred range of the flow rate of the mixed gas 
through the packed catalyst column is from 0.15 to 1.5 hr.sup.-1 in terms 
of liquid hourly space velocity. A practically complete reaction can be 
achieved by determining the flow rate of the mixed gas and the length of 
the catalyst column such that the contact reaction time becomes from 
several seconds to tens of seconds. Usually, a contact reaction time 
ranging from about 2 to 20 sec is sufficient and preferable. 
Benzaldehyde or a substituted benzaldehyde formed by this continuous 
hydrolysis reaction is passed through a cooler provided at the lower end 
of the reaction tube together with the unreacted portion of the steam and 
received in a suitable vessel in a cooled and condensed state. In most 
cases the compound as the reaction product is obtained in a state 
separated from the water (condensate of the unreacted steam), but in some 
cases the reaction product remains in a state suspending in water. In the 
latter cases the reaction product can be isolated by a simple solvent 
extraction method using a suitable organic solvent. The reaction product 
can be refined by a vacuum distillation method. 
The invention will be illustrated by the following examples 1-3 relating to 
the use of activated carbon catalyst treated with acid and examples 4-15 
relating to the use of activated carbon catalyst impregnated with a metal 
chloride or a metal sulfate. 
EXAMPLE 1 
An activated carbon catalyst was prepared by the steps of immersing a 
commercially available activated carbon, which passed through a 4-mesh 
sieve and retained on a 10-mesh sieve, in 95% sulfuric acid for 2 hr at 
room temperature, washing the activated carbon withdrawn from the acid and 
air-drying the washed activated carbon at 80.degree. C. for 3 hr. In a 
reaction tube a packed catalyst column was provided by packing 25 ml of 
the acid-treated activated carbon catalyst in a section of the reaction 
tube. 
Water and benzal chloride were continuously introduced into a vaporizer by 
using metering pumps, respectively. The feed rate of water was 0.37 g/min, 
and that of benzal chloride was 0.33 g/min. The vaporizer was maintained at 
230.degree. C. and connected to the aforementioned reaction tube, in which 
the packed catalyst column was kept heated at 180.degree. C. 
While the mixed gas discharged from the vaporizer passed through the packed 
catalyst column, the vaporized benzal chloride and steam in the mixed gas 
underwent a catalytic contact reaction. The reacted gas was condensed in a 
cooler to obtain a liquid suspension, and the suspension was subjected to 
ether extraction. The extract was dried, deprived of ether by distillation 
and then subjected to reduced-pressure distillation in a nitrogen gas 
atmosphere. 
The above described process was continued until the quantity of benzal 
chloride subjected to reaction reached 100 g. Obtained as the result was 
64.0 g of benzaldehyde containing no trace of tar as a possible 
by-product. The yield of benzaldehyde was 97.2% of theory. 
EXAMPLE 2 
The activated carbon mentioned in Example 1 was immersed in 95% sulfuric 
acid kept heated at 150.degree. C. for 3 hr, then washed with water and 
air-dried at 100.degree. C. for 3 hr. In a reaction tube a packed catalyst 
column was provided by packing 25 ml of the thus treated activated carbon 
in a section of the tube. 
In a vaporizer maintained at 250.degree. C., 0.19 g/min of water and 0.21 
g/min of m-chlorobenzal chloride were continuously vaporized. The 
resultant mixed gas was passed through the packed catalyst column which 
was kept heated at 200.degree. C. to cause catalytic contact reaction 
between the vaporized m-chlorobenzal chloride and steam in the mixed gas. 
The reaction was continuously carried out until the quantity of reacted 
m-chlorobenzal chloride reached 100 g. Obtained as the result was 69.1 g 
of m-chlorobenzaldehyde containing no trace of tar. The yield of 
m-chlorobenzaldehyde was 96.2% of theory. 
EXAMPLE 3 
Using the activated carbon catalyst described in Example 2 and under the 
same conditions as in Example 2, 0.18 g/min of water and 0.23 g/min of 
o-trifluoromethylbenzal chloride were continuously vaporized and passed 
through the packed catalyst column to accomplish hydrolysis of 100 g of 
o-trifluoromethylbenzal chloride in total. 
This process gave 71.0 g of o-trifluoromethyl benzaldehyde containing no 
trace of tar, so that the yield was 93.5% of theory. The boiling point of 
this product was 82.degree.-83.degree. C. at 40 mmHg. 
REFERENCE 1 
For comparison with Example 3, use was made of 50 ml of a catalyst prepared 
by firing .gamma.-Al.sub.2 O.sub.3 at 400.degree. C. for 5 hr in place of 
25 ml of the acid-treated activated carbon in Example 3. In other respects 
the vapor phase hydrolysis process of Example 3 was performed identically. 
In this case, the conversion of o-trifluoromethylbenzal chloride to 
o-trifluoromethyl benzaldehyde was about 25% when examined after the lapse 
of 1 hr from the start of the continuous reaction and lowered to only about 
5% after the lapse of additional 5 hr. 
REFERENCE 2 
In place of the acid-treated activated carbon used in Example 3, use was 
made of 25 ml of the activated carbon mentioned in Example 1 without 
treating it with any acid or any alternative. In other respects the vapor 
phase hydrolysis process of Example 3 was performed identically. 
When the quantity of o-trifluoromethylbenzal chloride subjected to the 
reaction reached 100 g, the conversion of this compound to 
o-trifluoromethyl benzaldehyde was only 1.5%. 
The process of Reference 2 was repeated generally similarly but by raising 
the reaction temperature to 350.degree. C. and extending the reaction time 
by 300 percent. In this case the conversion value increased to 34.7%, but 
it was found that phthalic acid was formed as a by-product due to the 
employment of a very high reaction temperature. 
EXAMPLE 4 
An activated carbon catalyst was prepared by the steps of immersing the 
activated carbon mentioned in Example 1 in a 20% (by weight) aqueous 
solution of ferric chloride for 24 hr at room temperature and air-drying 
the activated carbon withdrawn from the solution at 80.degree. C. for 3 
hr. In this catalyst, the amount of ferric chloride was 16% by weight of 
the activated carbon. 
The continuous vapor phase hydrolysis process of Example 1 was performed 
generally similarly but by using 25 ml of the chloride-containing catalyst 
prepared by the above described steps in place of the acid-treated 
activated carbon in Example 1. 
The reaction was continuously carried out until the quantity of benzal 
chloride subjected to reaction reached 100 g. As the result 64.1 g of 
benzaldehyde was obtained, so that the yield was 97.4% of theory. 
EXAMPLE 5 
The continuous vapor phase hydrolysis process of Example 2 was performed 
generally similarly except that 25 ml of the chloride-containing activated 
carbon catalyst described in Example 4 was used in place of the 
acid-treated activated carbon in Example 2. 
The reaction was continuously carried out until the quantity of 
m-chlorobenzal chloride subjected to reaction reached 100 g. As the result 
69.0 g of m-chlorobenzaldehyde was obtained, so that the yield was 96.0% of 
theory. 
EXAMPLES 6-14 
In these examples, the continuous vapor phase hydrolysis process of Example 
3 was repeated generally similarly except that the acid-treated activated 
carbon in Example 3 was replaced by different activated carbon catalysts 
in the respective examples as shown in the following Table. In every 
example the reaction was continued until the quantity of 
o-trifluoromethylbenzal chloride subjected to reaction reached 100 g. The 
yield values of o-trifluoromethyl benzaldehyde in Examples 6-14 are also 
presented in the Table. 
______________________________________ 
Yield of 
Metal Salt in 
o-Trifluoromethyl 
Activated Carbon 
benzaldehyde 
Catalyst Weight % of theory 
______________________________________ 
Example 6 
SnCl.sub.2, 33 Wt % of 
65.0 g 85.5% 
activated carbon 
Example 7 
NiCl.sub.2, 19 Wt % of 
63.3 g 83.4% 
activated carbon 
Example 8 
ZnCl.sub.2, 35 Wt % of 
66.8 g 87.9% 
activated carbon 
Example 9 
CuCl.sub.2, 35 Wt % of 
69.9 g 92.0% 
activated carbon 
Example 10 
MnCl.sub.2, 32 Wt % of 
72.1 g 94.9% 
activated carbon 
Example 11 
CoCl.sub.2, 25 Wt % of 
72.9 g 95.9% 
activated carbon 
Example 12 
FeCl.sub.3, 16 Wt % of 
73.0 g 96.1% 
activated carbon 
Example 13 
FeSo.sub.4, 14 Wt % of 
52.6 g 69.2% 
activated carbon 
Example 14 
CuSO.sub.4, 12 Wt % of 
70.0 g 91.9% 
activated carbon 
______________________________________ 
EXAMPLE 15 
In accordance with Example 4, the activated carbon was impregnated with 
ferric chloride such that the amount of ferric chloride in the resultant 
catalyst was 16 wt% of the activated carbon, and 25 ml of this catalyst 
was packed in a reaction tube to provide a packed catalyst column. 
In a vaporizer kept heated at 250.degree. C., 16 g/hr of water and 20 g/hr 
of o-trifluoromethylbenzal chloride were continuously vaporized. The 
resultant mixed gas was passed through the packed catalyst column which 
was kept heated at 200.degree. C. The vapor phase catalytic contact 
reaction was continuously carried out for 15 hr. 
The conversion of o-trifluoromethylbenzal chloride to o-trifluoromethyl 
benzaldehyde was examined at various time points during the total reaction 
time of 15 hr. In the single FIGURE, the curve A represents the result of 
the examination. 
REFERENCE 3 
A catalyst was prepared by the steps of immersing .gamma.-Al.sub.2 O.sub.3 
in a solution of 160 g of CuCl.sub.2.2H.sub.2 O in 160 g of water kept 
heated at 90.degree. C. for 2 hr, and heating the alumina withdrawn from 
the solution at 400.degree. C. for 2 hr. In this catalyst the amount of 
cupric chloride was 28.0% by weight of .gamma.-Al.sub.2 O.sub.3. 
The process of Example 15 was performed generally similarly except that 25 
ml of the alumina base catalyst prepared in the above described way was 
used in place of the activated carbon catalyst in Example 15. 
The conversion of o-trifluoromethylbenzal chloride to o-trifluoromethyl 
benzaldehyde was examined in the same manner as in Example 15. The result 
is represented by the curve B in the FIGURE. 
From a comparison between the curves A and B, it is apparent that the 
alumina base catalyst in Reference 3 was very low in its catalytic 
activity on the vapor phase hydrolysis of o-trifluoromethylbenzal chloride 
and, furthermore, underwent a very significant deterioration in its 
activity with the lapse of time.