136
FREEZE—DRYÏNG
us to screen thelarge number of possible quenching uids which we had gathered, especially
if we were to investigate each under a wide variery of quenching conditions. In addition, the
problem of reproducing the size and geometry of small pieces of tissue so that runs ton
different days could be compared was not solved. We decided to do the initial screening
‘
with metal thermoCouples and embedded these in 1—2-mm sections of hypodermic tubing
_
So that the ov'erallcooling rates were in the neighborhood of
per second+ä
regi0n comparable to that expected from sm'allpieces of tissue in good quenching media“:
"
Cooling/curves were recorded on Polaroid lm with an oscilloscopeca‘.merei, as describé‘d
in Rebhun,*(1965); The following halO‘carbons were
(usually the commerôiäl
rather—than Chemical name is given tosave'space) : F12 (freon 12), F13, F14, F22, Gene tron‘ 23,5
chloride, peruoropropane, mixtures of different proportions of F 13
Fl‘3 'ad22 and an aZeotropic
of
and
The hydrocarbôns investigated
Were, propane (several grades) ethane, ethyle11e,pr0pylene, i50pentane, isobutane, 2—methÿl
peut—am, butehe—l, and 3Àmethyl—'l-butenexln addition, miXtures of isoperit£me and proparie we’re tried
an azeotr0pi0mixtute Of propane'an‘d F22 (32 : 68). At rstÏwe
‘
tested a large number? of”insulatorïcoatsand
plus powders using primarily
liquid nitrogen itself as “the“ quenching ‘1ûid ashad
etïal (1961) and Luyet (1961)!
Similä.r“reSultS to theirS
increases in
tate up to 10
obtainable in pure liquid nit‘r‘ôgeWere
proper thickness coats and with
_
the proper
and powder,
3:
glÿcerol, vaseline,”
dibutyl phthalate, formvar_and a"“Väriety lof -oils.*Thejthickness of the coat was controlled
by using diéreht concentrations
dissolVèdin appropriate solvent and‘th‘en
dipping the thermocouple in and.
evap0rate. An optimum Was
;!
obtained with vaseline dipped
silica powær. “A large variety of nücleating
sites were tried including carbon powders (all poor with respect to this technique), cellulose ‘
;
powders, protein powders, silica powders, activated alumina,screencd into…di‘erentïsize
…;
categories and molecular sieve (Linde), ground in a ball mill and sieved. For the work with
‘
;
the:other1quenchi‘ngagents, vaseline and“:—dibutÿlphthàlate“ were chosen as insulators and
primarily Santocel (a15iliCaceous‘ ‘u‘ ’), or ,.gradedg‘sizes
_
powders orithe basis , of:£xperienCe with liquid nitrogen,
large number of trials,
run'andfsomething :_over %250‘phot0gŒph8=otïcooling eur—ves Fobtained, many With
'
254“Curvesiîo a photograph;ÿ The sun) total ofthis eXpe‘rience Can‘be sumæd up in one
pointiüng Statement :—-in no Case
we‘ able to:“ohtain freezing!rates…=faster than that in;
,
propane (at about
and:
Coat…_nor- p0Wder were»in:
any»way able,tofimprove ”ont—his.
good:as pro—?
,
pane and: both—ethane grand; ethylene were
the ::-proper.» coatings so that they
prbpane though there waszvariability. Isôpenta11eand:other hydr‘Îo>
'
—carbons with?ÿboilig
than:propane and when
acl;dedgtpropäe, alWays
Among :.the halocarbohs, Genetr0n :23‘:
,
_
,
(uoroform)
cooling rates:
…
=
Were approXihaaælyäâZü
23 aud‘xFtefonî 12
_
—,
;
,
=15‘4;‘5Ë
,
_
‘
'
“Of—88 and —— 129°C
_
,
'
Ÿ
FREEZE—DRYÏNG
us to screen thelarge number of possible quenching uids which we had gathered, especially
if we were to investigate each under a wide variery of quenching conditions. In addition, the
problem of reproducing the size and geometry of small pieces of tissue so that runs ton
different days could be compared was not solved. We decided to do the initial screening
‘
with metal thermoCouples and embedded these in 1—2-mm sections of hypodermic tubing
_
So that the ov'erallcooling rates were in the neighborhood of
per second+ä
regi0n comparable to that expected from sm'allpieces of tissue in good quenching media“:
"
Cooling/curves were recorded on Polaroid lm with an oscilloscopeca‘.merei, as describé‘d
in Rebhun,*(1965); The following halO‘carbons were
(usually the commerôiäl
rather—than Chemical name is given tosave'space) : F12 (freon 12), F13, F14, F22, Gene tron‘ 23,5
chloride, peruoropropane, mixtures of different proportions of F 13
Fl‘3 'ad22 and an aZeotropic
of
and
The hydrocarbôns investigated
Were, propane (several grades) ethane, ethyle11e,pr0pylene, i50pentane, isobutane, 2—methÿl
peut—am, butehe—l, and 3Àmethyl—'l-butenexln addition, miXtures of isoperit£me and proparie we’re tried
an azeotr0pi0mixtute Of propane'an‘d F22 (32 : 68). At rstÏwe
‘
tested a large number? of”insulatorïcoatsand
plus powders using primarily
liquid nitrogen itself as “the“ quenching ‘1ûid ashad
etïal (1961) and Luyet (1961)!
Similä.r“reSultS to theirS
increases in
tate up to 10
obtainable in pure liquid nit‘r‘ôgeWere
proper thickness coats and with
_
the proper
and powder,
3:
glÿcerol, vaseline,”
dibutyl phthalate, formvar_and a"“Väriety lof -oils.*Thejthickness of the coat was controlled
by using diéreht concentrations
dissolVèdin appropriate solvent and‘th‘en
dipping the thermocouple in and.
evap0rate. An optimum Was
;!
obtained with vaseline dipped
silica powær. “A large variety of nücleating
sites were tried including carbon powders (all poor with respect to this technique), cellulose ‘
;
powders, protein powders, silica powders, activated alumina,screencd into…di‘erentïsize
…;
categories and molecular sieve (Linde), ground in a ball mill and sieved. For the work with
‘
;
the:other1quenchi‘ngagents, vaseline and“:—dibutÿlphthàlate“ were chosen as insulators and
primarily Santocel (a15iliCaceous‘ ‘u‘ ’), or ,.gradedg‘sizes
_
powders orithe basis , of:£xperienCe with liquid nitrogen,
large number of trials,
run'andfsomething :_over %250‘phot0gŒph8=otïcooling eur—ves Fobtained, many With
'
254“Curvesiîo a photograph;ÿ The sun) total ofthis eXpe‘rience Can‘be sumæd up in one
pointiüng Statement :—-in no Case
we‘ able to:“ohtain freezing!rates…=faster than that in;
,
propane (at about
and:
Coat…_nor- p0Wder were»in:
any»way able,tofimprove ”ont—his.
good:as pro—?
,
pane and: both—ethane grand; ethylene were
the ::-proper.» coatings so that they
prbpane though there waszvariability. Isôpenta11eand:other hydr‘Îo>
'
—carbons with?ÿboilig
than:propane and when
acl;dedgtpropäe, alWays
Among :.the halocarbohs, Genetr0n :23‘:
,
_
,
(uoroform)
cooling rates:
…
=
Were approXihaaælyäâZü
23 aud‘xFtefonî 12
_
—,
;
,
=15‘4;‘5Ë
,
_
‘
'
“Of—88 and —— 129°C
_
,
'
Ÿ