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Патент USA US2112242

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29, 1938.
Filed March 19, 1936
sou RCE
.1 “
Patented Mar. 29, 1938
Benjamin Kramer, Samuel Natelson, and'Albei-t‘
E° Sobel, Brooklyn, N. Y.
- Application March 19, 1936, Serial No. 69,736
(01104-31) '
This invention relates to antirachitic vitamins \ antirachitic vitamin yield will be materially di
and, more particularly, relates to novel apparatus
for and methods of converting provitamins into
'minished. On the other hand, improper applica- ,
,tion of too high a potential for that frequency
antirachitic vitamins.
» etc. may result. in a. spark discharge .which will
Heretofore, several methods have been proposed
and used to antirachitically. activate foods and
sterols having no antirachitic potency. The most
destroy» the provita'mins. Application of fre- 5
quencies below or above the critical range also
reduces the ‘e?iciency of antirachitic conversion of \ Y
widely accepted process for antirachitically' acti-
the provitamins.
vating substances comprises exposure to a source
w .
We have found that the most economical pro
10 of ultra-violetJlight.’ Commercial production by
such a process‘ requires an expensive investment
in materials, particularly quartz. A quartz
duction of substances containing antirachitic vita- 10
mins is to activate ergosterol ‘or crudev cholesterol
and subsequently introduce a small percentage of
mercury arc lamp is used to generate ultra-violet
rays which are directed upon the substance in a
15 solid state or, more generally, in a suitable liquid
the activated sterols to foods and medicines, for
example yeast, olive oil, milk, cod liver oil and the‘ ' I
like. \The ergosterol or crude cholesterol is ap- 15
plied between the electrodes of the apparatus ac
cording to our present invention, preferably in- a
solid,loosely powdered state. In‘a‘nother form of
our invention, the sterols or provitamin is dis
' solved in a suitablesolvent as, for example, ether 00
solution contained in quartz ?asks or the like.
Production of ultra-violet light by sources other
than a mercury arc lamp, such as the glow dis‘ charge, open arc discharges or thecorona dison charge are relatively inefficient. Exposure of provitamins to open are or corona discharges results
in the destruction of the vitamin almost as rapidly.
as it is formed.v The other‘ proposed" methods for
antirachitically activating :provitamins are of
‘ 2;, mere laboratory. signi?cance on account of the
i very low e?icienoies of conversion together with
the expensive apparatus and the skilled manipulation required. These methods include: cxposure of the material .to Xrays; bombardment
30 ‘of the material by electrons in ajcathode ray
tube‘; subjection of the material to a high frequency alternating current greater than a
thousand cycles.
and introduced between the discharge electrodes “
in a fine spray; a
We_have found that the process according to
our presentinvention also, has a sterilizing effect
uponthefoodsor Substances subjected to it in that 2;,
bacteria, PrOtOZOa'aIId other micro-Organisms are‘
Foods which possess antirachitic
properties in a greater 01‘ less degree. such as milk,
olive oil, yeast, cod liver oil and the like, may be
directly activated‘ by the brushdischarge ap- 30
paratus of our present invention.
yAccordingly, an object of our invention is to
provide novel methods of converting provitamins
We have discovered a simple, inexpensive and‘ into antiratchitic vitamins. .
3;; very ef?cient method of'antiratchitically activat- .
Another object of our invention is to convert 35
ing provitamins by an electric discharge- By an provitamins into antirachitic vitamins by a brush
extended investigation of the action of the-difdischarge,
ferent types of electrical discharges through gases
uponprovitamins, We have" discovered that by
4o carefully Controlling the Various parameters. a
critical condition exists whereby the conversion of
‘ provitamins to antiratchitic vitaminsis extremely
‘ favorable. The Critical electri?al discharge, generally referred to as the brush discharge, performs
45 the efficient, antiratchitic conversion.
We ‘have
found that for a partlcular physlcal apparatus’ a
most favorable voltageexists, dependent upon the
‘A further object of our invention is to provide
simple, inexpensive and ef?cient apparatus for
and methods of converting provitamins such as
sterols into antirachitjc vitamins‘
still a further Object of our invention is to pro_
vide novel apparatus for andmethods of steriliz
mg food Substances_
These and other objects of Our'invention Wm 45
be evident in the following description in conne‘ci
“on with the drawin in which
. ‘
spacing of the electrodes between which the ma
terial is placed and thata most suitable frequency ,
13”‘? 1 is 3‘ Sc emanc dlagram usedtm the
so of application of the alternating current exists of descnptlon of elem-1? discharge phenomena‘ 50
the order of 250-350 cycles.
As will be explained
in ‘more detail hereinafter, a voltage below the .
critical ‘for a particular frequency, area and spacing of the plates and dielectric will produce a glow
5r, discharge instead of a brush discharge and the
‘through gases‘
Figure 2 is a qualitative graphical representa
tion of the Several gaseous electric discharge
Figure 3 is a modi?cation of Figure'l.
Figure 4 is a partial perspective illustration of a
preferred embodiment of our present invention.
Figure 5 is a qualitiative curve representing the
e?iciency of conversion ‘of provitamins to anti
rachitic vitamins withwrespect to the frequency
of the applied alternating current potential.
When a voltage is applied between two spaced
conductors having a gaseous atmosphere between,
a number of distinct types ‘of electrical discharges
10 may take place between the plates through the
gas dependent upon the nature and magnitude of
the potential applied to these plates. A variety
of phenomena accompanies gaseous electrical dis
charges including luminous, thermal, magnetic,
15 mechanical and chemical effects in varying de
by a voltage gradient which corresponds to sub
stantially the maximum voltage which can be
supported between the electrodes bounding the
region, other conditions remaining the same. We
further distinguish the “brush discharge” as the
electrical discharge occurring after the glow dis
charge, on increasing the voltage, and corre
sponds to the region characterized by the curve
portion 20 of Figure 2. The brush discharge cor
responds in Figure 2 to the discharge produced
in the vicinity of the peak voltage ea. Other con
ditions which aifect the particular “brush dis
charge voltage” for carrying out our process are
the frequency of the applied voltage, the spacing
of the bounding electrodes, the character of di
grees. In accordance with our present invention‘,
the chemical action of the electrical discharge is
electric material used and the gaseous condition
utilized and the conditions of operation are ad
within the discharge region.
of the other physical actions. This type of elec
The brush discharge is maintained‘ by careful
adjustment of the voltage for a given structure.
Increasing the electrical energy or current supply
to the electrodes causes the production of the
' trical discharge is known as the brush discharge.
spark discharge represented by region 1|. Region
In order to clearly set forth the critical param
eters for optimum antirachitic conversion ‘of the
25 materials, the following discussion as to the
22 represents the electric ?ame which results from
further increasing the current supply. Curve 23
justed so as to produce the type of discharge hav
20 ing a maximum chemical action and a minimum
several types of electrical discharge is presented.
Referring to Figure 1, two metallic plates l0 and
represents the negative voltage-current charac- :
teristic of the high tension arc and region 24
represents the low tension are as is well known by
II are spaced from each other by a ?xed amount,
for example, one centimeter. The space I! be
30 tween electrodes lil and II contains a gaseous
those skilled in the art. It is to be understood
that the graph plotted in Figure 2 is merely a
qualitative representation of the several types of
electrical discharge phenomena and that the ac
atmosphere for example ordinary air at atmos
pheric pressure. A variable high potential or tual voltage and current depend upon the type,
voltage source I3 is connected to plates l0 and Ii surface area and shape of the oppositely disposed
by corresponding conductors I4 and it.
electrodes, the spacing between said electrodes,
An ammeter “5 may be inserted in series with the type of gas and its temperature and pressure
as contained between the electrodes. ‘The type
conductor ii for observation of the current ?ow
ing during an electrical discharge between plates of voltage which produces the electrical discharge
characteristics represented in Figure 2 may be an
in and ii.
Figure 2 is a graph representing the variation in » interrupted direct current or an alternating cur
rent voltage. The frequency of the interruptions 40
the current of the discharge as indicated on am
meter l6 as plotted with respect to the variable or alternations of the voltage source should be
voltage applied between"-electrodes HI and II
‘ ‘Y with a ?xed spacing. At low voltages, for example
below one‘ thousand volts, practically no current
As the voltage
between the plates i0 and II is slowly increased,
45 will ?ow between the electrodes.
minute current will ilow between them as repre
sented by curve ii. The discharge I1 is charac
teristically non-luminous or invisible and is ac
companied by negligible chemical or other physi
cal e?ects. At a certain region I! which is defi
nite for given conditions of temperature, pressure
and electrode spacing the glow discharge begins
which represents a discontinuity in the graph.
Curve l9 represents the voltage-current relation
relatively low, for example, below a thousand
cycles, otherwise diiferent electrical actions will
occur. Asthe frequency of the voltage source is
increased, ‘the peak voltage supported, corre- ,
sponding to so of Figure 2, will be ‘lowered. An
increase in frequency will increase the current
?ow between the electrodes Ill-II due to a ca
pacitative or reactive current ?ow due to the func
tion of the plates |I|—_ll as an electrical con
The phenomena of the electrical discharge be
comes more complicated than the relatively sim
ple representation of Figure 2 when dielectric ma
terial is interposed between the electrodes ill-4 I. .
Referring to Figure 3, a glass plate 25 is placed
adjacent to the inner surface of electrode ill and
another glass plate 26 at the inner surface of
of the glow discharge. The voltage may be in
creased to a very high value and the glow dis
charge will still be maintained and the current
plate ii. A variable high potential alternating
will correspondingly increase. The glow dis
60 charge is accompanied by a characteristic lumi
current source 21 is applied to the conductors 60
i4--II. If the generator 21 is operated at two
nosity which includes ultra-violet light.
As the voltage is further increased, it will reach hundred cycles and the voltage applied to the
a peak value 80 which is practically the\maximum electrodes Ill and II is increased until the brush
voltage which the electrodes i0--Il can‘ support v‘discharge corresponding to curve 20 in Figure 2
65 for a particular gaseous atmosphere and spacing. “ occurs, it will be found that the brush discharge 65
The glow discharge disappears at the 'region 20 will occur when the electrodes l0 and I l arecloser
and the characteristic brush discharge occurs. together than the corresponding case where no
The brush discharge has sometimes also been dielectric plates 25-26 are used. If the plates l0
called the silent discharge or the dark discharge. and i l of Figure 3 are separated a distance equal
to that described in connection with Figure 1, 0
70 These terms are misnomers since the brush dis
charge is neither silent nor dark for it is attended namely one centimeter, then the maximum vol
tage corresponding to an of Figure'2 will be greater
by a peculiar sound and by some light.
at the brush discharge. The higher voltage is
By the term “brush discharge” as used herein
after in the speci?cation and claims, we refer to due to the presence of the dielectric material,
75 the electrical discharge produced across a region
namely the glass plates 25—26 interposed be 75
tween the electrodes i0 and II which act to re
duce the. potential gradient through the atmos
within the actual brush discharge for antiarchit
I icl conversion. _ Experiments'have shown that if
phere as is well known in the art. However, ‘it is
evident that a brush discharge may be produced
between two electrodes as long as ,a gaseous at
mosphere exists between them,‘ and that it is
theprovitamin ‘substance 35 be placed at‘ the
outer ‘regions of‘ the annular space, namely the
regions 36 and 3'! immediately outside of the di
rect . electrostatic‘ ?eld; negligible antirachitic
difficult to‘ express the value of the voltage to be vitamin conversion] results, demonstrating ab
applied for all conditions. If the frequency of
generator 21 is increased, the maximum voltage
sence of" ultra violet light conversion.
. An important feature‘ of our present invention
‘ ‘The critical spacing of the electrodes ‘maybe
resides in the “use .of a critical frequency for the‘
most‘ e?icient antirachitic conversion of the pro
vitamin substance‘; We" have ~discovered that for
supply as follows: The electrodes l0 and II, with
sterols, the optimum frequency range of conver
which a given discharge structure can support
will be lessened.»
determined foraparticular voltage and frequency most _, provitamin substances,‘ particularly the
s the dielectric materials 25 and 26 in place (Fig. 3)
if required, are connected to the supply and are
ognizable spark discharge begins. The electrodes
below 250 cycles, as vwell as for frequencies above
350‘ cycles. Figure 5 is a qualitative curve rep
are then slowly moved apart until the spark dis
charge just disappears. The brush discharge will
vitamin substances" to ' antira‘c‘hitic vitamins plot
gradually brought together until the easily rec
sion occurs between ‘250 and, 350 cycles. The ‘effi
ciency of"conversion" decreases with frequencies
then be evident to those. skilled in the art.
7 >
We have ‘discovered that provitamins placed
in the electrostatic, ?eld within a brush discharge
are efficiently converted into antirachitic vita- ‘
25 mins. We have also found that the antirachitic
conversion is relatively insigni?cant for electri
cal discharges occurring at the lower, voltages,
namely the non-luminous discharge ‘represented
by curve I‘! .in Figure 2 and the glow discharge
resentation' 38 of the relativenconversion of pro
ted withv re’spectfto the frequency of the applied
poteritialin cycles per second‘.
It ishto be understood that a brush discharge
occurs along the'points of curve 38 for the vari
ous frequencies plotted. At zero frequency a rel
atively'veiy small yield occurs’. As the frequency
is increased to 250 cycles, the yield correspond
ingly increases until the maximum. As the fre
quency is. further increased to about 350 cycles,
30 represented by curve l9; and that the discharges ‘ the efficiency of vcon/version continues near the
occurring beyond the brush discharge,v namely maximum. For particular substances, a peaked
nature of curve 38; will be evident" at a single
the spark ‘discharge and the electric are dis
charges represented by curves 2|, 22, 23 and 24 ] critical frequency in ‘the order of 250-350 cycles.
of Figure 2 actually destroy the provitamins. It ‘ However, inFigure ,5,’we have, not" attempted to
accurately represent any’ particular case but
is to be, understood thatthe brush discharge rep
tov give an approximate conception of the
resents an electrochemical ‘conversion of thepro
vitamin to the antirachitic vitamin. This elec “effect and range of thefrequency of the voltage
trochemical action is analogous to the production generator 32' upon" the ef?ciency of conversion.
of ozone-which has ‘also been found to be most For frequencies of the applied voltage to produce 40
the brush, discharge above 3.50'cycles, the effi
40 efficient in the brush discharge region.
ciency of conversion diminishes until at 1000'
cycles and above, the efficiency is relatively small.
As seen by curve 38 of Figure 5 "approximately
electrodes as
tubes provided
in Figured.
with metal
.An outer,
foil: 50% ofthe maximum efficiency or yield occurs
with frequencies in the range'of 150 to 550 cycles
cylindrical glass tube 28 is provided with a me
In a preferred embodiment for carrying out the ,
process of our present invention, we utilize two
per second. By choosing the intermediate fre_
quency range‘ of'250‘ to 350 cycles‘ per second
30 is coated with a metallic sheet or foil electrode _, the maximum efficiency or yield is approached.
30 upon its inner surface. The annular-distance ,For most provitamin substances a frequency of ~
between concentric tubes 28 and 30 is optional about 300 cyclesper secon'd'will produce best 50
tallic plate or foil electrode 29 attached to its‘
outer surface. The inner concentric glass tube
and determines the volume capacity of the appa- .
ratus. The metallic electrodes 29 and 3| are
connected to a suitable alternating current volt
age source 32 by conductors 33-34.
Ergosterol 35 or other suitable provitamin-ma
terial is placed between the glass cylinders 28
If a solid'state of the substance is used,
it should be in a loosely powdered form.
The ,
‘value of the voltage from electric source 32 ap
60 plied between electrodes 29 and 3| is predeter
mined, so as to produce a brush discharge there
It is, necessary for a gaseous atmosphere to
prevail between ,thedischa'rge electrodes, there
fore the solidprovitam'in 35 should be in a loose
ly powdered state. When air is used, ,ozoneis
formed during the activation process according
to our invention. , Ozone 'orjtheaction of the
oxygen itself acts 'to‘slowly decompose the vita
' mins and accordingly somewhat reduce the yield.
We have found thatv if the'activation process be
tween the concentricvtubes __28_ and 30 is carried
One must be careful that the. voltage ' on in the presence of an inert gas such as nitro-,
applied to the apparatus produces the true ‘brush
discharge corresponding to curve 20 of Figure 2.
If the current is too low, the inefficient glow dis
charge represented by curve 19 will take place;
if the current is too high, a. spark discharge rep
resented by curve 2| will take placeand destroy
any vitamins that might-be formed. In a par;
ticular example, glass cylinders 28 andf30 of one
millimeter thickness and with an annular space
of two millimeters required a voltage of the order
of 8000 volts to produce a brush discharge.
__ We have found that it is necessary to place the
provitamin substance 35 in the electrostatic ?eld I
gen thev efficiencyof conversion is materially in
creased.v Nitrogen may either be' continuously
.passed'through the substance‘ "35 being activated
in ‘the annular chamber or may be con?ned to .
‘the annular chamber if it is‘ made gas tight as
will be understood by‘ythoseskilled' in the art.
1N0 activation is'obse'r'ved ‘ifv a solution ‘of pro
vitamin' fills the annular space, since a brush
discharge cannot be‘ established 'thru the solvent.
A modi?cation for activating the ergosterol 01'
other 'provitamin resides incontinuously spray
ing it in the formof a ?nev d'us't between the an
nular space’of‘a relatively vlong structure. The
ergosterol, crude cholesterol or other provitamin
substance may be dissolved‘in a suitable solvent
such as ether or alcoholand passed through the
brush discharge in the annular space in the form
feed this into a transformer designed to raise the
voltage to the desired range. A condenser board
is used in connection with the final transformer
so as to keep the current and voltage in phase. /
The ergosterol or crude cholesterol is a concen
of a ?ne spray." Antirachitic conversion ‘of pro- '
vitamins to vitamins is evident with an exposure
trated antirachitic vitamin source, It is too
potent for direct consumption. Smallv amounts
are administered or eaten, preferably in combina
tion with a. food or medicine. A small percentage
provitamin substance will increase the yield. Ex
posure of a half hour will in most cases give a of the activated material is mixed with cod liver
oilyyeast, milk or other edible substance. No
maximum yield consistent with commercial pro
duction. However, we do not restrict our process change in taste or odor of the food occurs. The
to the time of exposure which depends upon the antirachiticpotency of the edible material treat
shape and size of the ‘apparatus as well as the ed in this manner is equivalent to direct activa
type and form of provitamin‘ substance being. tion thereof. It is much more economical to
produce edible or medicinal antirachitic sub
Another important factor for increasing the stances by adding a small percentage of concen—
as low as two minutes.
Increasing the time of
exposure to a predetermined maximum of the
e?iciency of conversion'is the temperature at
trated antirachitic vitamin content material to
which’ the conversion takes place.
the substances, as compared to direct activation
thereof. It is to be understood that antirachiti 20
It is preferable
to carry out the process at a temperature of about
vcally potent substances may be directly activated
inaccordance with our present invention.
This application is a continuation in part of
of the whole apparatus, and therefore of the sub- ‘
stance 35 being converted, may be maintainedcool our application Serial No. 723,314, filed May 1,
0° C. although good results will be obtained at
ordinary room temperatures. The temperature
by means of a fan directly blowing thereon or
We claim:
1. The process for antirachitically activating
provitamins which comprises introducing pro
the apparatus. ' Other suitable forms of cooling
will also be evident to thoseskilled in the art. - vitamin material into a gaseous region and apply
The true nature of the electro-chemical action ing a voltage gradient across the gaseous region 30
containing the provitamin material for'producing
during the brush‘ discharge has been in contro
versy for some time in the art. However, in the a gaseous brush discharge about the provitamin
present case, the activation appears to be due material, whereby the provitamins are converted
preferably by the continuous circulation of cool
ing water through the central circular tube 30 of
to the impingement of ions or activated atoms or
into antirachitic vitamins by the brush discharge
moleculesproduced within the brush discharge
acting on the provitamin material in the gaseous .
from the gaseous dielectric, upon the provitamin
substance which release their energy to the pro
production of a brush discharge; ‘placing a pro
vitamin substance such as ergosterol or crude
containing the provitamin particles for producing
a gaseous brush discharge about the provitamin
cholesterol within the brush discharge preferably
particles, whereby the provitamins are converted
into' antirachitic vitamins by the interrupted
brush discharge acting on the provitamin par 45
ticles in the gaseous region, and cooling the dis
charge region to about 0“ centigrade to increase
the efficiency of conversion.
3. The process for antirachitically activating
?ne dust spray, or a spray of a solution of pro
vitamin substance through‘ the brush discharge;
preferably maintaining an inert gaseous atmos
phere such as nitrogen and keeping the substance
coolpreferably at 0° C. The production of'the
brush discharge should be determined for each
particular structure designed. The necessary
voltage is determined'by the shape of the elec
trodes, their size and their spacing. Thefre
quency of the applied voltage should preferably
provitamins which comprises introducing pro- _
‘vitamin material _in a powdered and loosely
packed form into a gaseous region and applying
a voltage gradient across the gaseous region con- '
taining the provitamin powder at substantially
the maximum voltage which the region can sup~ , ,
be in a most efficient range for conversion. gen
port for producing a, gaseous brush discharge
about the provitamin material, whereby the pro
erally within 250 and 350 cycles. A suitable
source of the high voltage alternating current
necessary for carrying out our process will be
evident to those skilled in the art. An alternat
ing current generator connected to a step-up
vitamins are converted into antirachitic vitamins
by the brush discharge acting on the provitamin
material in the gaseous atmosphere.
‘4. The process for antirachitically activating
provitamins which comprises continuously pass
transformer will provide the necessary high volt
ing a solution of provitamin material as a fine
vitamin particles into a gaseous region and apply
ing a. voltage gradient across the gaseous region
vitamin substance structure, or in the form of
vitamin, converting it to the antirachitic vitamin.
The important factors for the production of
antirachitic vitamins from provitamins are the
insulated from the metallic electrodes by glass
plates or the like; using a loosely powdered pro
2. The process for antirachitically activating
provitamins which comprises introducing pro
The alternator is adjusted to the proper ‘ spray through a gaseous region and applying a
optimum frequency. For small quantity produc
voltage gradient across the gaseous region con
tion, an induction coil adjusted to, for example,
250 cycles of ‘interruption, may bepused to main
taining the provitamin spray at substantially the
maximum voltage which the region can support
tain the brush discharge in an apparatus con
for producing a gaseous brush discharge about
structed to operate with the voltages, for example
8000 volts, presented at the output thereof.
A convenient way of producing the desired fre
quency and voltages is to generate the frequency
the provitamin material, whereby the provitamins
by one of the usual types of variable audio oscil- .,
5. The process for antirachitically activating
provitamins which comprises introducing pro
lators, to amplify this by means of the standard
types of pie-‘ampli?ers and ampli?ers and to
are converted into antirachitic vitamins by the
brush discharge acting on the provitamin ma
vitamin material into an inert gaseous'region'and
9,1 19,242
8. The process of antirachitically activating
applying a voltage gradient across the gaseous
region containing the provitamin material at
substantially the maximum voltage which the
vprovitamins which comprises introducing provi
tamin material into a gaseous region and apply
ing a voltage gradient across the gaseous region
region can support for producing a gaseous brush
containing the provitamin material at substan
discharge about the provitamin material, whereby
tially the maximum voltage which the region can
support for producing a gaseous brush discharge
about the provitamin material, and generating
the brush discharge with an alternating ‘voltage
having a frequency of. about 300vcycles per second, 10
whereby the provitamins are converted into anti
rachitic vitamins by the brush discharge acting
.the provitamins are converted into antirachitic
vitamins by the brush discharge acting on the
provitamin material in the inert gaseous atmos~
6. The process for antirachitically activating
provitamins which comprises introducing provita
min particles into a region of nitrogen gas and
applying a voltage gradient across the gaseous
on the provitamin material in the gaseous atmos
region containing the provitamin particles at sub
stantially the maximum voltage which the region
charge about the individual provitamin particles,‘
'7. The process of antirachitically activating
provitamins which comprises introduci g provi
tamin material into a gaseous region and applyihg
25 a voltage gradient across the gaseous region con-
provitamins which comprises introducing provi
tamin particles into a gaseous region and apply
ing a voltage gradient across the gaseous region
can support vfor producing a gaseous brush dis
whereby the provitamins are con, erted into anti
rachitic vitamins by the brush‘ discharge acting on
20 the provitamin particles in the hi ogen atmos-\
- '
9. The process for antirachitically activating
containing the provitamin particles at substan
tially the maximum voltage which the region can 20
support for producing a gaseous brush discharge
about the individual provitamin particles, and
generating the brush discharge with an alternat
ing voltage having a frequency in the range of
‘ 150 to 550 cycles per second, whereby the provi
taining the provitamin material for producing a
gaseous brush discharge about the provitamln
material, and, generating the brush discharge with
tamins are converted into antirachitic vitamins
by the alternating brush discharge acting on the
provltamin particles in the gaseous atmosphere,“
an interrupted current having about 300 inter
ruptions persecond, whereby the provitamins are
‘converted into antirachitic vitamins by the inter- -
rupted brush discharge acting on the provitamin
material in the gaseous atmosphere.
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