Effect of water properties in thixotropic clay systems on biological activit

Low, P. F.

English

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A N N U A L  R E P O R T  
TO 
NATIONAL AERONAUTICS AND 
SPACE ADMINISTRATION 
ON 
EFFECT OF WATER PROPERTIES 
I N  THIXOTROPIC C U Y  SYSTEMS 
ON BIOLCGICAL ACTIVITY 
(Contract No. NGR 15-007-004) 
Submitted by 
D r .  Philip F. Low 
Department of Agronomy 
Purdue University 
West Lafayette,.  Indiana 
(THRU) (ACCESSION NUMBER) 
72’77~ -57-7- (CODE 
(NASA CR OR TMX OR AD NUMBER) (CATEGORY) 
, i  GPO PRICE $ 
CFSTI PRICE(S) S 
Hard copy (HC) -9, 
c Microfiche (M F) 
ff 653 July 65 
https://ntrs.nasa.gov/search.jsp?R=19670008438 2020-03-16T18:36:34+00:00Z
2. 
This project was activated on January 1, 1965. However, Dr. Brian 
assigned to it, did not G. Davey, the Post-Doctoral Research Associate 
arrive until the end of January. 
essential to the project, was not received from France until about April. 
Between the time of his arrival and the receipt of the microcalorimeter, 
Dr. Davey became acquainted witn the literature related to the problem and 
prepared a large quantity of Na-saturated, Wyoming bentonite (clay). When 
the microcalorimeter arrived he began immediately to install it. However, 
it was found that the rooms reserved for the microcalorimeter had to be 
remodelled extensively before it could be put into operation. 
ling consumed considerable time. 
prevented the satisfactory operation of the recording equipment that accom- 
panied the instrument. Consequently, recording equipment of a different 
type was ordered. 
was encountered with ground loops and shielding. After this difficulty was 
overcome, it was found that one of the thermopiles in the microcalorimeter 
had been damaged slightly in transit and produced too much electrical noise. 
Therefore, new matched thermopiles (a differential technique is employed) 
The Calvet microcalorimeter, which was 
The remodel- 
Then it was found that building vibrations 
When the latter equipment was put in operation, difficulty 
were requested from the manufacturer. 
their arrival. 
entirely to install them. 
which was indispensable to the program, was not operating successfully until 
Customs clearance in New York delayed 
And it was necessary to disassemble the microcalorimeter 
The net result was that the microcalorimeter, 
the end of September. 
experience had to be gained relative to its use. 
Thereafter, it had to be accurately calibrated and 
Since Dr. Davey had to 
.. 
3. 
leave in Janu d y, 19 too little time was left for him to perform more 
than preliminary experiments with it. However, the preliminary experiments 
gave exciting results. They, and other experiments not involving the 
microcalorimeter, are reported hereafter. 
During the measurement of the relative partial molar free energy of 
water in clay s o l s  and gels with an osmometer, it became apparent that the 
magnitude of the osmotic pressure of these systems was dependent on the 
size of the pores in the membrane. 
membranes and the construction of a new miniature osmometer that employs a 
transducer to measure the osmotic pressure and a potentiometric recorder to 
record it. With this instrument osmotic pressures of colloidal suspensions 
can be measured to less than a an. of water in a few hours. And less than 
0.5 ml. of suspension is required. 
will have extensive use in future work in this and other laboratories. 
This led to an examination of different 
It is anticipated that this osmometer 
To determine the minimum clay concentration at which gelation occurs in 
a clay-water suspension, a Fann viscosimeter was used. The results showed 
that essentially no torque was exerted on the viscosimeter bob, when the 
surrounding suspension was set in motion by the rotor, until the suspension 
contained 4 percent clay by weight. Then the torque increased rapidly with 
clay concentration. Hence, the minimum concentration of clay required for 
gelation was assumed to be 4 percent. 
-4 The NaCl activity was measured in suspensions containing 10 N NaCl - 
and different concentrations of clay. This activity was measured with a 
4. 
Ag-AgC1 electrode and a sodium-ion electrode couple. 
a c t i v i t y  was plot ted against  the  clay concentration, two s t r a igh t  l i nes  
having d i f fe ren t  slopes were produced. The in te rsec t ion  of these l i nes  
was a t  4 percent c lay by weight. 
changes the N a C l  a c t iv i ty .  It i s  postulated t h a t  t h i s  change i n  a c t i v i t y  
i s  the  r e su l t  of the change i n  water propert ies  t h a t  accompanies gelation. 
Gel strengths of c lay pastes having d i f fe ren t  p r io r  mechanical t r e a t -  
When the N a C l  
Therefore, it i s  evident t h a t  gelat ion 
ments were also determined i n  the viscosimeter. 
injected in to  the viscosimeter from an 18-ga~ge hypodermic needle had 
greater gel  strength than those remolded and introduced w i t h  a spatula.  
Spinning the pastes between the rotor and bob reduced the ge l  strength 
but j a r r ing  them subsequently increased it again. 
increased by allowing the system t o  stand undisturbed when the space between 
the rotor  and bob was large.  However, very l i t t l e  increase i n  ge l  s t rength 
occurred when t h i s  space was small. The viscosimeter study i l l u s t r a t e s  the  
f a c t  t h a t  the s t a t e  of a clay-water system depends on i t s  his tory.  
f a c t  must be taken in to  account i n  a l l  future  studies.  
It was found t h a t  pastes  
The ge l  strength was 
This 
When heats of gelation were determined i n  the microcalorimeter on 
these same pastes,  it was found that  those injected in to  the calorimetric 
c e l l  from the 18-gauge needle had essent ia l ly  no heat of gelation. The 
same was t rue  of those pastes that  had been ja r red  vigorously. Evidently 
these pastes were i n  t h e i r  equilibrium s t a t e s .  Since the needle in jec t ion  
would have oriented the f la t  c lay par t ic les  i n  a p a r a l l e l  array,  it may be 
5 .  
assumed that one equilibrium state has this kind of particle arrangement. 
Evidently, this state has relatively great shear strength. Those pastes 
that were remolded and introduced into the calorimetric cell with a 
spatula, or that were stirred in the cell, exhibited heats of gelation. 
Heat was given out on gelation at 25OC; it was taken in at 3OoC. It is 
believed that the heat given out at 25OC. represents the true heat of 
gelation. However, the heat taken in at 3OoC. is not likely due to 
gelation per - se because it is contrary to tine first law of thermodynamics 
for a system to spontaneously increase in energy. 
case, the temperature of the paste was raised from room temperature to 
3OoC. only a little while before it was introduced into the cell of the 
microcalorimeter, it is postulated that heat was required to evaporate 
dissolved gases so that gas-vapor equilibrium could be re-established at 
the new temperature. 
Since, in the latter 
However, more work in this regard needs to be done. 
Although very little is known about the effect of hydrogen bonding 
on thermal conductivity, it has been postulated that an increase in 
hydrogen bonding should increase this quantity. k higher degree of 
hydrogen bonding is believed to exist in the water in a clay ge~l than 
in a clay sol .  
the thermal conductivities of a clay suspension at different times after 
stirring it (the clay suspensions having more than 4 percent clay by 
weight gelled on standing). 
observed with time. 
Therefore, a miniature thermal probe was used to determine 
No difference in thermal conductivity was 
Therefore, either no change in the structure of the 
6 .  
water occurred as the gel developed or thermal conductivity is relatively 
insensitive to changes in water structure. 
In order to study the effect of changes in water properties in a clay 
system on biological activity, a culture of Streptococcus faecalis in TDY 
broth was introduced, in equal amounts, into two suspensions having the 
same clay content. One of these suspensions vas injected into one cell 
of the microcalorimeter through an 18-gauge hypodermic needle. The other 
was stirred and poured into the opposing cell. 
a gel; the latter was a sol. The two cells were used in a differential 
arrangenent so that the difference in heat produced by the metabolizing 
microorganisms could be measured. 
produced by the microorganisms in the gel than by those in the s o l .  
However, there was a question about the adsorption of components of the 
TDY broth on the particle surfaces and the resulting influence this might 
have on the structure of the adjacent water. Infra-red analysis indicated 
little or no adsorption. 
experiments should be performed to see how much concentration of the broth 
could be reduced, t o  minimize adsorption, without reducing the heat produc- 
The former suspension was 
The result was that more heat w&s 
But in order to be safe, it was decided that 
tion of the organisms below a measurable amount. 
time to perform these experiments under the present contract. 
the following experiments were conducted instead. 
There was insufficient 
Therefore, 
Clay suspensions were introduced into cells of the microcalorimeter 
by injection through an 18-gauge hypodermic needle and with a spatula. 
7. \ \ 
\ 
> The l a t t e r  suspensions had been spun i n  the viscosimeter p r io r  t o  t h e i r  
introduction in to  the  calorimetric ce l l s .  Therefore, they were more f l u i d  
than the former. 
suspension i n  each c e l l .  
v idual  systems. 
a d i f f e ren t i a l  technique. All the  r e su l t s  indicated t h a t  the germination 
r a t e  was about 20 percent greater i n  the gels  than i n  the  so-called sols, 
Then 10 le t tuce  seeds were placed on the  surface of the  
Heats of germination were measured on the indi-  
Also differences i n  heats of germination were measured by 
i . e . ,  the more-fluid suspensions. These r e s u l t s  strongly suggest t ha t  
water properties a r e  d i f fe ren t  i n  clay sols than i n  c lay gels  and t h a t  
biological  a c t i v i t y  i s  influenced by t h i s  difference.  However, since some 
trouble was encountered i n  aerat ing the  seeds and since more de f in i t i ve  
information must be obtained about the s t a t e  of water i n  the systems pre- 
pared as  described, fur ther  study of t h i s  phenomenon i s  warranted. 
In  addition t o  what has been described heretofore,  special  heaters,  
c e l l s ,  e tc . ,  were designed and b u i l t  fo r  experiments on spec i f ic  heats,  
heats  of compression and heats  of condensation of water i n  so l s  and gels .  
Further, preliminary measurements of specif ic  heats  and heats  of compression 
were made. The r e s u l t s  were encouraging. However, there  was insuf f ic ien t  
time t o  conduct more detai led experiments pr ior  t o  D r .  Davey's departure. 


Effect of Water Properties in Thixotropic Clay Systems on Biological Activity Annual Report, 1965

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