U.S. patent number 3,873,274 [Application Number 05/329,022] was granted by the patent office on 1975-03-25 for titrator.
This patent grant is currently assigned to Merck Patent Gesellschaft mit beschrankter Haftung. Invention is credited to Karlheinz Neisius.
United States Patent |
3,873,274 |
Neisius |
March 25, 1975 |
Titrator
Abstract
A titrating device adapted to be removably air-tight fitted onto
a bottle of titrating liquid, comprising a graduated plunger-type
syringe, for mounting externally on the bottle by a seal providing
air-tight communication with a burette of comparable capacity as
the syringe, for mounting in the bottle, so that titrating liquid
in the bottle is metered into the burette and does not contact the
syringe when the plunger is withdrawn while the tip of the burette
is below the surface of the titrating liquid.
Inventors: |
Neisius; Karlheinz (Darmstadt,
DT) |
Assignee: |
Merck Patent Gesellschaft mit
beschrankter Haftung (Darmstadt, DT)
|
Family
ID: |
5834764 |
Appl.
No.: |
05/329,022 |
Filed: |
February 2, 1973 |
Foreign Application Priority Data
Current U.S.
Class: |
422/75; 422/517;
73/864.16; 604/186; 604/407; 422/921 |
Current CPC
Class: |
B01L
3/0206 (20130101) |
Current International
Class: |
B01L
3/02 (20060101); G01n 001/10 (); G01n 001/14 () |
Field of
Search: |
;23/259,292,253
;128/26,218C,220 ;73/425.4P,425.6 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Reese; Robert M.
Attorney, Agent or Firm: Millen, Raptes & White
Claims
What is claimed is:
1. A titrating device comprising a container for a liquid to be
titrated, said container having an opening through a neck bearing
external threads, separable means for withdrawing said liquid from
said container including a burette for depending into said
container, a graduated plunger-type syringe for standing above said
container, and hollow sealing means interconnecting said burette
and said syringe in air-tight communication, the volume of said
syringe being not substantially greater than the volume of said
burette, and said sealing means including an upwardly extending
tubular portion having an integral annular ring on the external
surface thereof, and a screw cap for mounting on said threaded neck
and having an aperture therein for receiving said tubular portion
therethrough, said screw cap interacting with the upper surface of
said annular ring for forcing the lower surface of said ring
against said neck for sealing said separable means with said
container.
2. The titrating device of claim 1 wherein said burette has a
barrel in the form of a right circular cylinder and wherein said
container includes an annular collar mounted in the neck thereof
for scraping liquid from the surface of said burette as said
burette is separated from said container.
3. A titrating device according to claim 1 wherein said syringe
includes a cylindrical barrel portion and wherein said device
includes a transparent plastic sleeve surrounding the barrel of the
syringe and wherein said barrel and said surrounding sleeve are
inserted into said upwardly extending tubular portion of said
sealing means in an air-tight friction fit.
Description
BACKGROUND OF THE INVENTION
This invention relates to novel titrating devices.
It is conventional to employ pipetting droppers for rapid titration
determinations in which the determination is based on the number of
droplets of the titrating liquid consumed in the titration. As the
accuracy of the dropprs increases, the less difference there is in
the individual droplets with respect to their weight. Analytical
error increases, the larger the size or the greater the number of
droplets which are involved in the respective determination.
It has been found that a wide margin of error must be tolerated in
such determinations using conventional pipetting droppers, because
the droplets delivered by the same pipetting dropper are not always
of equal weight, due to different wetting of the surface from which
the droplets are released or the effects of the environment on the
surface tension of the liquid to be released in droplet form.
Another reason for inaccuracy is that it is practically impossible
to manufacture a plurality of pipetting droppers which all deliver
droplets of identical weight.
Therefore, it has been suggested to execute such titrations with a
graduated plunger-type syringe, rather than with a pipetting
dropper. In such a case, the volume of the liquid consumed in the
titration is the determining factor, rather than the number
(weight) of the released droplets. However, a disadvantage in the
use of such a syringe is that when the titrating liquid is sucked
into the syringe, an air bubble forms underneath the plunger of the
syringe, which is difficult to remove, particularly in case of
plastic syringes. In order to eliminate the air bubble, which is
required in order to calibrate the syringe to the zero point, the
syringe must be inverted and a portion of the titrating liquid
squirted out of the syringe, which can then run over the fingers of
the person using the syringe. This is dangerous, in particular, in
case of corrosive or toxic titrating solutions. Moreover, the
outside wall of the syringe must then be cleansed in some cases to
prevent the inadvertent release of traces of the titrating liquid
from the outer wall of the syringe during the titration, which
would affect the accuracy of the determination. Consequently, such
syringes have not become popular as auxiliary titrating means for
rapid determination methods.
It has now been found that the above-described disadvantages can be
eliminated by the specific arrangement of the titrating device of
this invention.
SUMMARY OF THE INVENTION
The titrating device of this invention comprises a graduated
plunger-type syringe, adapted for mounting outside a container for
a titrating liquid by a hollow sealing means providing an air-tight
communication between the syringe and a burette adapted for
mounting inside the container by the sealing means to withdraw
liquid from the container. Preferably, the syringe is disposed
vertically above the burette.
DESCRIPTION OF THE DRAWING
The drawing is a vertical cross-section of a preferred embodiment
of the titrating device of this invention mounted onto a container
for the titrating liquid.
The embodiment shown in the drawing comprises a plunger-type
syringe 1 having a plunger 1a and a barrel 1b with indexing indicia
1c on its wall and ending in a tip 1d; an annular gasket or washer
sealing means 2 with a sleeve-like tubular extension 2a and an
annular shoulder 2b; a sealing cap 3 with an axial aperature 3a in
its top for a container 4 for the titrating liquid; a burette 5
with a lip 5a on its upper end and a dispensing tip 7 at its lower
end; a transparent plastic tube or sleeve 6 fitted onto the barrel
1b of syringe; and a scraper 8 mounted in the mouth 4a of container
4.
Syringe 1 is mounted axially vertically above burette 5 and in
indirect air-tight communication therewith by gasket 2 fitted into
the mouth 4a of container 4 and, by means of annular shoulder 2b on
the upper portion of gasket 2 immediately below extension 2a, over
the top of the mouth 4a of container 4. Lip 5a of burette 5 is
fitted into the lower end of aperature of gasket 2 so as to be
proximate to the lower tip 1d; of barrel 1b of syringe 1. Container
4 and cap 3 are threaded so that the syringe assembly can be
rigidly mounted on the container, the tightening of the cap forcing
the shoulder 2b against the neck 4b of the container 4.
To withdraw a specific amount of titrating liquid from container 4,
plunger 1a of syringe 1 is first depressed downwardly into barrel
1b and thereafter the titrator is fitted onto the storage vessel 4.
During this step, the air trapped in the burette 5 prevents the
entrance of titrating liquid into the glass tube 7. When plunger 1a
of syringe 1 is moved upwardly, preferably after screwing cap 3
tightly onto container 4, i.e., partially withdrawn from barrel 1b,
an amount of liquid corresponding to the change in volume of
syringe 1 enters burette 5. In this manner, an exact titration can
thereafter be effected, with this exactly metered quantity of
liquid, by moving plunger 1a of syringe 1 downwardly, so that the
titrating liquid exits from tip 7 of burette 5. The thus-consumed
volume of liquid can be read off from the graduation scale 1c on
the wall of barrel 1b of syringe 1.
The volume of the glass tube forming burette 5 projecting into the
titrating liquid in container 4 is preferably equal to or larger
than that of the syringe 1 so that no titrating liquid can enter
syringe 1, even with a full utilization of the volume capacity of
syringe 1. The avoidance of any contact between the titrating
liquid and syringe 1 is especially of interest when the titration
is to be conducted with corrosive liquids, e.g., concentrated acids
or bases. In this manner, the lifetime of the syringe 1 is
prolonged, particularly if the plunger is provided with a
gasket.
In many cases it has proved furthermore advantageous to surround
the syringe 1 with an optional transparent plastic tube or sleeve
6. This protects the graduation which is normally printed on the
outside of the barrel of the syringe and, because of a certain
magnifying effect, facilitates the reading of the graduation and
thus enhances the accuracy of the determination.
Any desired, commercially available plunger-type syringe can be
employed as syringe 1. Of special practicability in handling are
syringes of a synthetic resin, e.g., polyethylene or -propylene,
having a volume of between about 1 ml. and 20 ml. The container 4
can be formed of any desired inert material. Preferably, a
conventional glass or plastic bottle is used.
Sealing means 2 can be formed of any material which is resistant to
the titrating liquid employed. Suitable materials are, for example,
rubber or elastomeric synthetic resins. As stated above seal 2
connects the upper rim of burette 5, which desirably is bent a
little outwardly to form a lip 5a which ensures an air-tight fit,
and the lower part of syringe 1 so that an air-tight seal is
obtained. Sealing means 2 is disposed within the sealing cap 3. In
order to impart extra ruggedness to the apparatus and to ensure an
air-tight fit, seal 2 advantageously has a sleeve portion 2a which
extends beyond the cap 3 to such an extent that it encloses the
lower portion of the syringe 1 and sleeve 6.
Sealing cap 3 can be of any desired shape, for example, a screw
cap. The cap need merely form a liquid tight closure for the
associated container and must be resistant to the titrating liquid
employed. The sleeve-like extension 2a of seal 2 projects through
aperature 3a of cap 3.
Scraper 8 is advantageously mounted within the mouth of the
container 4 so that it contacts the outer wall of burette 5.
Scraper 8 can be made of cotton wool, glass wool, synthetic resin
lips or a similar inert material, depending on the titrating liquid
utilized. The only essential point is that the scraper removes any
residual titrating liquid which may adhere to the outer wall of
burette 5 when the titrator is removed from container 4.
Burette 5 suitably terminates at its bottom end in a tip 7 so that
the metering accuracy is increased. Burette 5, like the other
components of the titrator, can be made of glass or inert synthetic
resin. The capacity of the burette, i.e., its internal volume,
advantageously is the same as or greater than that of syringe 1 to
ensure that no titrating liquid is drawn into the latter.
Syringe 1 preferably is arranged vertically above burette 5.
Syringe 1 can, however, project at an angle with respect to burette
5, e.g., by forming a bend in sleeve 2a, if this should be
advantageous for certain applications. One need only ensure that a
tight seal is effected by sealing means 2 providing communication
between burette 5 and syringe 1.
This novel and easily maintained titrator is very suitable for
conducting rapid analyses, which methods have gained increasing
importance nowadays. A wide field of application is in the analysis
of foodstuffs and of water for general use and waste water. Among
the many possible uses for the novel titrator are the determination
of the total and carbonate hardness in various types of water, the
determination of disinfecting chlorine in swimming waters, the
determination of the hydrazine content of boiler feed water, the
determination of the free and bound sulfurous acid, the total
acidity of wine, and the determination of free fatty acids in
baking shortening.
It has been established that with the aid of the novel device,
results are achieved whose accuracy is comparable with that of
conventional laboratory methods.
From the foregoing description, one skilled in the art can easily
ascertain the essential characteristics of this invention, and
without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *