US2535477A - Method of fabricating thermometers - Google Patents

Description

Dec. 26, 1950 E. c. ANDRAE METHOD OF FABRICATING THERMOMETERS Filed April 24, 1946 i Carl Rndrae.

ENTofi RM A' '1 Patented Dec. 26, 1950 METHOD OF FABRICATING THERMOMETEES Ernst Carl Andrae, Stockholm, Sweden Application April 24, 1946, Serial No. 664,579 In Sweden October .19, 1.944

'7 Claims. (01. 29-1482) dis is well known, a protective gas, most frequent-ly nitrogen, is generally introduced into thermometer tubes instead of atmospheric air, inasmuch as the oxygen of the air is apt to oxidize the mercury and other substances contained therein, the oxides thus formed soiling the capillary tube and rendering the reading of the thermometer difficult. Hitherto, the filling of the protective gas into the thermometer tube has only been efiected by mechanical means, the thermometer having been. connected to a gas receptacle and sealed upon having been filled with the gas. This is also believed to be the reason of the fact that hydrogen gas has not been used, which gas would otherwise be the most suitable per se owing to its reducing effect. If hydrogen would be filled-in in this way, a great risk of explosion would be incurred on account of the possibility of the formation oi oxyhydrogen gas.

The present invention refers to a particularly simple and safe method of introducing an ar" bitrary protective especially hydrogen, into thermometers and the like. The invention is substantially characterized by the fact that one or more substances capable of developing the gas in consideration are introduced into the thermometer tube, whereupon the latter is sealed by melting.

The accompanying drawing illustrates by way of example three different stages of the method according to the invention.

Fig. l is an elevational view partly in section of the tube before constriction occurs;

Fig. 2 is an elevational view partly in section of the tube after constriction has occurred at one place, and

Fig. 3 is an elevational view partly in section of the tube after constriction has occurred at two places.

The capillary tube i, which contains mercury, is provided at the top with a tubular extension 2 of a much greater internal diameter. After the mercury has been filled-in, a piece of sodium 3 is dropped into the tube 2 (Fig. 1). The latter is then constricted by melting or softening above the piece of sodium, as at i, and preferably also at the upper end to such a degree that only narrow openings will remain. Melting or softening can be effected by means of a gas flame,and compressed or constricted by a suitable tool when in the softened condition. Thereafter a small quantity of water 5 is introduced through the upper opening 5 into the tube 2, said Water quantity remaining on account of its surface tension in or at the opening 4 (Fig. 2). After the water has thus been introduced, the tube 2 is scaled by .melting at the upper end 5 thereof, the Whole being then preferably turned upside down, so that the piece of sodium falls down toward the opening l so as to be brought into the proximity of the water, although it is not brought into contact therewith owing to the small diameter of the opening. The water now evaporates, and the vapour is absorbed by the piece of sodium, so that sodium oxide and hydrogen are formed. The quantities of water and sodium are so chosen that the desired pressure, say 25 atmospheres, is obtained. When the tube is then again turned by into its proper position, the piece of sodium oxide generally remains at the opening 4 by sticking to the glass wall (Fig. 3).

If desired, the tube may be evacuated or filled with some gas under normal pressure, for instance with nitrogen, before the hydrogen is introduced in the manner described, but this is not of any material importance, for if the air is caused to remain and the hydrogen introduced has a pressure of 25 atmospheres, for example, the partial pressure of the oxygen will be less than 1% of that of the hydrogen.

It is also possible first to introduce the water and then the sodium. Instead of sodium, other hydrogen-replacing metals may also be used, it being possible generally to make use of a plurality of substances other than water and metal, which are capable of developing hydrogen or some other suitable gas on having been introduced into the thermometer or the like.

Having now described my invention, what I claim as new and desire to secure by Letters Patcut is:

1. A method of fabricating a thermometer containing hydrogen under pressure wherein a first reactant comprising water and a second reactant comprising a hydrogen-replacing metal capable of reacting with the water to form hydrogen are added to thermometer tube, which comprises adding one of the reactants to the tube, con- U stricting the internal diameter of the tube at a point in the tube above the location of said reactant, adding the other reactant into said tube above said constriction, sealing the tube at a point in the tube above the other reactant, and bringing the two reactants into proximity so that the reaction proceeds and the hydrogen is generated in the tube.

2. A method of fabricating a thermometer containing hydrogen under pressure wherein sodium and water are added to the thermometer tube above the mercury therein to react with one anwater remaining at said constriction in the tube,

sealing the tube at a point therein above the water, and rotating the longitudinal axis of the tube through 180 whereby the sodium and the water are brought into close proximity and the reaction.

proceeds to generate hydrogen in the tube.

3. A method of fabricating a thermometer containing hydrogen under pressure wherein sodium and water are added to the thermometer tube above the mercury therein to react with one another and form the hydrogen within the tube, comprising adding the water to the tube, constricting the internal diameter of the tube at a point in the tube above the location of the water therein, adding the sodium into said tube said sodium remaining at said constriction in the tube, sealing the tube at a point therein above the water, and rotating the longitudinal axis of the tube through 180 whereby the sodium and the water are brought into close proximity and the reaction proceeds to generate hydrogen in the tube.

4. A method in accordance with claim 1 wherein the said tube is evacuated prior to the addition of the reactants.

5. A method in accordance with claim 2 wherein the said tube is evacuated prior to the addition of the sodium thereto.

6. A method in accordance with claim 3 wherein the said tube is evacuated prior to the addition of the water thereto.

'7. A method in accordance with claim 1 wherein air in'the said tube is replaced by nitrogen prior to the addition of the reactants.

ERNST CARL ANDRAE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,823,452 Heron Sept. 15, 1931 2,106,495 Debor Jan. 25, 1938 2,361,413 Font Oct. 31, 1944 2,365,285 McDill Dec. 19, 1944 2,379,342 Cozzoli June 26, 194-5

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