JPH03109948A - Burette tip for volumetric titration - Google Patents

Abstract

PURPOSE:To accurately perform volumetric titration by forming a tubular member of the material having water repellency and constituting a tipped nozzle of this tubular member. CONSTITUTION:The lower end part 11 of a burette tip 10 is gradually narrowed to a conical shape and a tipped nozzle 12 formed of water-repellant material is fitted to the tip thereof. A tube 14 made of fluororesin is connected with the upper end part of the burette tip 10 via a screw joint 13. Titration liquid sent from a burette cylinder is discharged from the tip of the burette tip 10. A bubble reservoir 15 is formed near to the upper end of the burette tip 10. The bubbles contained in titration liquid sent from the burette cylinder are stored in the inside thereof. Thereby titration error is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] - The present invention relates to a bilulet used for volumetric titration, and in particular to improvements in the nozzle of the bilulet tip.

[Prior Art] In the volumetric titration method, a so-called billet is used to add a titrant to a sample solution. This volumetric titration bilulet has a nozzle at the tip of its bilulet tip, and the titrant is dripped from this nozzle. Further, in an automatic titration device, an electric billet is used and the discharged titrant liquid is integrated by electrical means, but in this case, the tip of the billet tip is generally immersed in the sample solution.

This is because if a part of the titrant liquid discharged from the bilulet tip does not mix with the sample solution and remains at the tip of the bilulet, the amount of titrant liquid discharged and the amount of titrant liquid actually mixed with the sample solution may differ. This is because a difference occurs, which adversely affects titration accuracy.

Due to the surface tension of the titrant, it is unavoidable that a small amount of the titrant remains at the tip of the bilulet tip, so by immersing the tip of the bilulet tip in the sample solution, the titration solution dispensed from the bilulet can be easily removed. The idea is to ensure that all of the liquid mixes with the sample solution.

[Problems to be Solved by the Invention]However, with the above-mentioned prior art biulet tip for volumetric titration, when the tip of the biulet tip is immersed in the sample solution, even when no discharge pressure is applied to the titrant solution. ,
The titrant solution will diffuse into the sample solution little by little from the tip of the billet. For this reason, there is a problem that an error occurs in the volume of the titrant liquid that is integrated and the titrant liquid that is actually mixed with the sample solution, and that it is difficult to obtain an accurate titration end point.

On the other hand, in order to solve this problem, it has been proposed, for example, to make the tip of the billet tip thinner to prevent the sample solution and titrant from mixing. The resistance of the flow path when discharging the titrant is large. This has a problem in that it has an adverse effect on the discharging speed of the titrant and slows down the titration speed.

SUMMARY OF THE INVENTION In view of the problems in the prior art described in (-), the present invention aims to provide a system that does not adversely affect the discharging speed of the titrant from the bilulet tip, and that allows the tip of the bilulet tip to be immersed in the sample solution to increase the volume of the titrant solution. To provide a biulet tip for volumetric titration that prevents the titrant from diffusing into the sample solution from the small hole at the tip of the biulet tip even when titration is performed, and thereby enables accurate volumetric titration. be.

[Means for Solving the Problem] That is, the object of the present invention is to provide a volumetric titration billet tip in which the tip nozzle is immersed in a sample solution and a titrant is dropped therein, in which the tip nozzle has water repellency. This is achieved by a volumetric titration billet tip characterized in that it is constructed of a tubular member made of a material that is commonly used.

[Function] According to the volumetric titration billet tip described above, the tip nozzle, which is immersed in the sample solution and drops the titrant, is composed of a tubular member made of a water-repellent material. As described below, even if the tip nozzle of the billet tip is immersed in the sample solution, the titrant will diffuse through the small hole in the tubular member, or the sample solution will react with the titrant in the small hole. is prevented.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a volumetric titration tip that is an embodiment of the present invention. The volumetric titration billet tip 10 is made of a transparent material such as Pyrex glass, and has an elongated tube shape as shown in the figure. Also, this billet chip 10
The lower end 11 of the nozzle 11 gradually tapers into a conical shape, and a tip nozzle 12 made of a water-repellent material is attached to the tip.

A tube 14 made of, for example, fluororesin is connected to the upper end of the billet chip 10 via a threaded joint 13. The titration liquid sent from the cylinder is discharged from the tip of the billet tip 10. Also, a so-called bubble reservoir I5 is formed near the upper end of the billet tip 10, and the titration liquid sent from the billet cylinder is discharged from the tip of the billet tip 10. The structure is such that air bubbles contained in the liquid are stored therein, and only the titrant liquid is dripped into the sample solution from the tip nozzle 12 of the billet tip 10.

Next, FIG. 2 shows the detailed structure of the tip nozzle 12 attached to the tip of the lower end portion 11 of the billet tip 10. As shown in FIG. As is clear from this cross-sectional view, the wall surface constituting the lower end 11 of the billet tip 10 gradually tapers into a conical shape, and a small hole 16 is formed at its tip. The tip nozzle 12 is attached to this small hole 16 as described above. This tip nozzle 12 is made of a water-repellent tube, for example, a tube made of a so-called fluororesin such as polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, copolymerized fluororesin, etc. This fluororesin tube is cut to a predetermined length, inserted into the small hole 16, and fixed. The fluororesin has water repellency, which is the property of repelling liquid. In a billet tip equipped with such a tip nozzle 12, even if the tip is immersed in a sample solution, as will be described later,
The titrant liquid in the billet tip IO is transferred to the tip nozzle 12.
This prevents the sample solution from diffusing outside through the small hole 17 or entering the small hole 17 and reacting with the titrant.

Experiments conducted on the performance of the tube made of the above-mentioned fluororesin and the results will be explained in detail below.

First, as an experimental method, in order to be able to numerically compare the degree of diffusion from the tube, the titration cell was filled with a) 1/100 normal hydrochloric acid (HCI) solution as a reagent. ) ■ A specified sodium hydroxide (NaOH) solution was filled into an experimental biuret chip, and the following experiment was conducted.

c) Titration was performed using a PH stat, and the pH was set at 4°00.

2) Without applying discharge pressure to the solution in the billet chip,
The tip of the tip was immersed in a hydrochloric acid solution for 20 minutes, and the titer was printed out every minute for measurement.

e) The titration amount for the first minute was subtracted from the amount of sodium hydroxide (NaOH) attached to the tip of the tip.

First, as a comparison of tube materials, the above experiment was conducted on tubes made of glass as well as the above fluororesin, and the results were as shown in Table 1 below.

As is clear from the above results, for the same tip inner diameter Table 1 d (diameter), the amount of diffusion per unit cross-sectional area of the fluororesin tube is 0. 08110. 196mm2=
0.1.58, while when using a glass tube it was 5. 80510, 196mm2 =
29.62, which clearly shows that the fluororesin tube has smaller diffusion than the glass tube, making it an excellent tube material.

Furthermore, in the case of a fluororesin tube, the smaller the inner diameter d at the tip, the smaller the amount of diffusion, but in consideration of the flow path resistance when discharging the titrant, a diameter of about 0.5 mm is preferable.

Next, for each length of the fluororesin tube, 9- Table 2 shows the results of the experiment.

Table 2 As is clear from this result, if the inner diameter is the same, there is almost no difference in the results when the length 1 is in the range of 10 to 50 (mffi). However, the last I ”
1. , 5 (mm), the titration value, that is, the diffusion is large.

The shape of the tip of the billet tip in the case of l=L, 5 (+nm) is shown in the attached FIG. 3.

The length I of the tube has an inner diameter of 0.5H,
l=5! It has been confirmed that this effect can be obtained if the temperature is I11 or higher.

10- Next, as another embodiment of the present invention, a tip nozzle having a shape shown in the attached FIGS. 4 and 5 was prepared.

First, the tip end nozzle 12 shown in FIG.
(mm), d=0. 5 (mm). The tip nozzle 12 shown in FIG. 5 is also made of fluororesin, and has a flange-like protrusion 18 at its tip, the dimensions of which are I=44.
(mm), d=0. 5 (mm). The measurement results for the tip nozzles of these Examples are shown in Table 3 below.

Table 3 As is clear from Table 3, it is confirmed that almost the same effects as in Example II shown in FIGS. 1 and 2 can be obtained by the other embodiments described above.

[Effects of the Invention] As is clear from the above description, according to the present invention, the dispensing speed of the titrant from the bilulet tip is not adversely affected, and the tip of the bilulet tip is immersed in the sample solution. Even when performing volumetric titration, there is extremely little titration error due to the titrant reacting by diffusing into the sample solution from the small hole at the tip of the billet tip, allowing for accurate volumetric titration. Can provide billet chips.

[Brief explanation of drawings]

FIG. 1 is a front view including a partial cross section showing the overall structure of a bilulet tip for volumetric titration according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of the tip of the bilulet tip for volumetric titration.
FIG. 3 is a cross-sectional view showing the shape of the tube at the tip end of the tip used in the experiment, and FIGS. It is a sectional view showing the shape of a tube.

Claims (3)

[Claims] (1) A burette tip for volumetric titration in which a tip nozzle is immersed in a sample solution and a titrant is dropped, characterized in that the tip nozzle is constituted by a tube-shaped member made of a water-repellent material. Buret tip for volumetric titration. (2) The burette tip for volumetric titration according to claim 1, wherein the water-repellent tubular member constituting the tip nozzle is made of fluororesin. (3) The burette tip for volumetric titration according to claim 1, wherein the water-repellent tubular member constituting the tip nozzle has an axial length of 5 mm or more.