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1. 14 6 2 Melting Plateau 14 6 2 1 Realizing the Melting Point in a Bath 14 6 2 2 Realizing the Melting Point in the 9230 Maintenance System 17 6 3 Correction for Pressure Difference 18 i 1 Before You Start 1 1 Symbols Used Table 1 lists the International Electrical Symbols Some or all of these symbols may be used on the instrument or in this manual Hart Scientific Manual Rev 140901 1 1 Before You Start Symbol Description AC AC DC Battery CE DC Double Insulated Electric Shock Fuse PE Ground Hot Surface Read the User s Manual Off On Table1 International Electrical Symbols 1 2 Safety Information Use this instrument only as specified in this manual Otherwise the pro tection provided by the instrument may be impaired The following definitions apply to the terms Warning and Caution Warning identifies conditions and actions that may pose hazards to the user Caution identifies conditions and actions that may damage the in strument being used Warnings To avoid possible electric shock or personal injury follow these guide lines Gallium is caustic Consult the metal manufacturer s MSDS Material Safety Data Sheet Federal law prohibits carrying this cell in the passenger section o2. Guide for complete information on how to use the maintenance device with the Model 5943 Gallium Cell 6 2 Melting Plateau Realizing the melting point can be performed in a bath or in the Model 9230 Maintenance System as described below 6 2 1 Realizing the Melting Point in a Bath A stable and long a few days melting plateau during which a great amount of thermometers can be calibrated is easy to obtain if you follow the instructions described below Put the cell into the maintenance bath at a temperature of 0 5 C below the melting point Hart manufactures a Model 7011 bath with a special cell support and SPRT preheat holder for the purpose of maintaining the gallium cell see Figure 2 Use silicone oil 200 05 or 200 10 as the bath fluid Light mineral oil Hart Model 5011 oil can be used instead of silicon oil Use the same oil in the entrant well to provide adequate heat transfer 14 Manual Rev 140901 5943 6 Operation Hart Scientific Manual Rev 140901 15 6 Operation Reentrant Tube Protective SST Case High Purity Metal Sample PTFE Crucible Liquid Sample Solid Sample Figure 3 Idealized Liquid Solid Equilibrium State of a Gallium Cell between the cell and the thermometer The oil level in the well should be approximately the same level 52 mm below the top of the cell as that of the gallium in the cell when the thermometer is in place in the well With some care distilled water can be used ins
3. than 25 C If the instructions in this manual are carefully followed the Model 5943 Gallium melting point cell will provide years of accurate use Hart Scientific Manual Rev 140901 11 5 Care and Handling Guidelines 12 Manual Rev 140901 5943 5 Care and Handling Guidelines 6 Operation 6 1 Freezing the Gallium The three methods for freezing the gallium cell slow freeze fast freeze and automated freeze are described in the following sections 6 1 1 Slow Freeze Method In order to freeze all the gallium in the cell immerse the cell in an ice bath or a bath with a temperature close to the ice point First immerse only one fourth of the cell in the bath thirty minutes later immerse half of the cell in the bath and another thirty minutes later immerse the three fourths of the cell in the bath Because of the large super cool of gallium even though the temperature of the gallium in the cell declines to a temperature near 0 C all gallium might still remain in the liquid state for a period of time Therefore monitor the temperature in the cell by us ing an SPRT When the cell is placed in an ice bath the temperature indi cated by an SPRT in the cell decreases fast at first and then decreases Hart Scientific Manual Rev 140901 13 6 Operation SET HEATER MODE DOWN UP EXIT HIGH LOW POWER COOLING HEATING High Precision Bath O I O I Figure 2 Maintenance Bath Model 7011 with Ga
4. well When the thermal equilibrium between the thermometer and pure gallium is reached approximately 20 min utes start the measurements See Figure 3 for the idealized liquid solid equilibrium state of a gallium cell at the start of the melt A typical melting curve is shown in Figure 4 If the bath temperature is set at 0 1 C above the melting point the melting curve will last for more than ten days If the 16 Manual Rev 140901 5943 6 Operation bath temperature is set at 0 01 C above the melting point the melting curve will last for more than two months 6 2 2 Realizing the Melting Point in the 9230 Maintenance System The user should be familiar with the following details before using the Model 9230 Maintenance System The Model 9230 is designed to automate the gallium cell melting pro cess This melting process is accomplished through the use of the Auto Program a microprocessor controlled program that determines set tem peratures scan rates duration times Peltier module configurations and melt heater controls By controlling these parameters in the proper order a temperature profile can be maintained in the block assembly that as sures a uniform melt maintains the melt over long periods of time prop erly refreezes the cell and keeps the cell ready for the next melt cycle The only attempt in describing the melting process in this manual is to provide a simple overview For complete details on realizing the melti
5. 5943 GalliumMeltingPointCell User sGuide Rev 140901 Rev 140901 Copyright 2001 All Rights Reserved Hart Scientific 799 E Utah Valley Drive American Fork Utah 84003 9775 Telephone 801 763 1600 Fax 801 763 1010 Internet http www hartscientific com E mail support hartscientific com Table of Contents 1 Before You Start 1 1 1 Symbols Used 1 1 2 Safety Information 2 1 3 Customer Service Information 2 2 Introduction 5 3 Specifications and Environmental Conditions 7 3 1 Specifications 7 3 2 Environmental Conditions 7 3 3 Warranty 7 4 Construction 9 5 Care and Handling Guidelines 11 6 Operation 13 6 1 Freezing the Gallium 13 6 1 1 Slow Freeze Method 13 6 1 2 Fast Freeze Method 14 6 1 3 Automated Freeze Method
6. ES EX PRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OR MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR USE HART SHALL NOT BE LIABLE FOR ANY SPECIAL INDIRECT INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSS WHETHER IN CONTRACT TORT OR OTHER WISE 8 Manual Rev 140901 5943 3 Specifications and Environmental Conditions 4 Construction The Model 5943 gallium melting point cell consists of a stainless steel outer shell a stainless steel cap with an entrant well a Teflon cell body containing the high purity gallium and a nylon lid with nylon entrant well Figure 1 Gallium expands on freezing by 3 1 requiring the cell to have flexible walls Teflon is a suitable material from this point of view but Teflon is gas permeable over time Over a four year period com pletely sealed Teflon cells drift about 0 5 mK under normal use There fore a stainless steel outer case is used to keep gas tight in the cell All of the parts and material used to construct the cell were carefully cleaned to avoid any contamination to the high purity gallium The high purity gallium was first sealed into the Teflon nylon body in a pure argon 99 999 atmosphere The pressure of argon in the body was adjusted to approximate 101 325 kPa at the melting temperature The actual value of this pressure was recorded and is reported on the Report of Test for the cell The correction for pressure difference from the standar
7. a period as stated in our current product catalog from the date of shipment This war ranty extends only to the original purchaser and shall not apply to any product which in Hart s sole opinion has been subject to misuse alter ation abuse or abnormal conditions of operation or handling Hart Scientific Manual Rev 140901 7 3 Specifications and Environmental Conditions Software is warranted to operate in accordance with its programmed in structions on appropriate Hart products It is not warranted to be error free Hart s obligation under this warranty is limited to repair or replacement of a product which is returned to Hart within the warranty period and is de termined upon examination by Hart to be defective If Hart determines that the defect or malfunction has been caused by misuse alteration abuse or abnormal conditions or operation or handling Hart will repair the product and bill the purchaser for the reasonable cost of repair To exercise this warranty the purchaser must forward the product after calling or writing Hart for authorization Hart assumes NO risk for in tran sit damage For service or assistance please contact the manufacturer Hart Scientific Inc 799 East Utah Valley Drive American Fork UT 84003 9775 Phone 801 763 1600 Fax 801 763 1010 E mail support hartscientific com THE FOREGOING WARRANTY IS PURCHASER S SOLE AND EXCLU SIVE REMEDY AND IS IN LIEU OF ALL OTHER WARRANTI
8. d value of 101 325 kPa is calculated according to the actual pressure in the cell see Section 6 3 Correction for Pressure Difference The assembled Teflon nylon body was then encased into the stainless steel outer shell The stainless steel top with the entrant well was joined to the stainless steel outer case using argon arc welding The assembled cell was then connected to a vacuum system and pumped for more than ten hours During the pumping period the cell was purged with high purity argon many times Finally the cell was filled with 99 999 pure argon and sealed at almost the same pressure as that in the Teflon nylon body Hart Scientific Manual Rev 140901 9 4 Construction 10 Manual Rev 140901 5943 4 Construction Reentrant Tube Protective SST Case High Purity Metal Sample PTFE Crucible Figure 1 Construction of Gallium Melting Point Cell 5 Care and Handling Guidelines The Model 5943 gallium melting point cell is a delicate device Care must be taken in handling using and transporting the cell Keep the gallium in the cell in a solid state whenever possible Store the cell in the vertical position and in a safe place The surrounding temperature should be at least 4 C below the melting point e g 25 C or lower Special care must be taken during transportation of the cell Keep the gallium in the solid state Store the cell in a vertical position Keep the surrounding temperature lower
9. defined to be 29 7646 C by the ITS 90 making it an intrinsic temperature standard The MPGa is highly reproducible You can get almost the same tempera ture wherever and whenever you realize the MPGa The differences among the different realizations might be well within a few tenths of a millikelvin if you carefully follow the instructions given in Supplementary Information for the ITS 90 Comite Consultatif de Thermometrie CCT Bureau International des Poids et Mesures BIPM 1990 For your convenience Hart has developed a series of sealed cells and new techniques for the MPGa which make it easier to realize the MPGa The Model 5943 stainless steel cased MPGa cell is a new member of the Hart MPGa sealed cells series The Model 5943 reserves all of the bene fits of the Model 5903 including extremely low uncertainty Stainless steel is used as case material in the Model 5943 instead of the Pyrex glass used in the Model 5903 Therefore the Model 5943 is much more durable compared with the Model 5903 The Hart sealed cells will assist you immensely in realizing the MPGa in your laboratory The MPGa is an important fixed point for the calibration of a standard platinum resistance thermometer SPRT The ITS 90 specifies two subranges i e from 0 C to 29 7646 C and from 38 8344 C to 29 7646 C in which SPRTs must be calibrated at the MPGa Checking the stability of a temperature probe used mainly near room temperature at the MPGa is ve
10. essure Correction Equation t C C x P P C Pa 29 7646 0000172 20 10 8 0 Pressure Correction Example The pressure of argon P at the melting point in the gallium point cell is 91 325 Pa as given on the calibration certificate t C C x Pa C Pa 29 7646 0000172 20 10 10000 8 t C C C 29 7646 0000172 00002 18 Manual Rev 140901 5943 6 Operation Thus t C 29 764628 Hart Scientific Manual Rev 140901 19 6 Operation
11. f a commercial airline See MSDS in the back of this manual Cautions To avoid possible damage to the instrument follow these guidelines Read the section entitled Care and Handling Guidelines before remov ing the gallium melting point cell from the case Incorrect handling can damage the cell The gallium melting point cell must be kept in a vertical position Placing the cell in a horizontal position can damage the cell and void the warranty 1 3 Customer Service Information Hart Scientific can be contacted by writing to Hart Scientific Inc 799 E Utah Valley Drive American Fork UT 84003 9775 Or by calling or faxing Telephone 801 763 1600 Fax 801 763 1010 Our World Wide Web site is http www hartscientific com E mail support hartscientific com 2 Manual Rev 140901 5943 1 Before You Start When calling Hart Scientific Customer Service please have the following information available Model Number Serial Number Hart Scientific Manual Rev 140901 3 1 Before You Start 4 Manual Rev 140901 5943 1 Before You Start 2 Introduction The melting point of gallium MPGa at 29 7646 C is one of the defining fixed points of the International Temperature Scale of 1990 the ITS 90 The MPGa is the phase equilibrium between the liquid phase and solid phase of pure gallium at a pressure of one standard atmospheric pres sure i e 101 325 Pa The temperature of the MPGa is
12. llium Cell Insert slowly at last the temperature stops decreasing After a period of time the temperature raises a signal that the gallium starts freezing Finally the temperature decreases again and all of the gallium is frozen Once frozen the cell may be transferred to a maintenance bath such as the Hart Model 7011 see Figure 2 6 1 2 Fast Freeze Method The fast freeze method is based on NIST Technical Note 1265 Start with the fixed point cell at room temperature Use liquid nitrogen to super cool two or three solid copper rods for insertion in the entrant well The copper rods should be only slightly smaller than the inside diameter of the en trant well For example the Hart Model 5943 gallium cell has an entrant well with an inside diameter of 8 2 mm The solid copper rods should have a diameter of approximately 7 0 mm Insert the two or three super cooled copper rods into the entrant well successively to induce nucle ation As soon as the rods have been used to induce nucleation place the cell in an ice bath for at least one hour or longer Monitor the freeze with an SPRT Once the freeze has been achieved place the cell in a maintenance bath such as the Hart Model 7011 see Figure 2 6 1 3 Automated Freeze Method The Hart Scientific Model 9230 Maintenance System is specifically for the Model 5943 Gallium Cell The Model 9230 has a fully automated sys tem for maintenance of the Model 5943 Refer to the Model 9230 User s
13. ng point in the 9230 Maintenance System see the Model 9230 User s Guide In the Auto Program the Model 9230 stabilizes at 29 27 C to allow the gallium cell to equalize After equalization the program initiates the melt The block temperature is set to initiate a melt on the outer surfaces of gallium within the cell At the appropriate time the unit beeps and the dis play flashes Htr on to indicate that the inner melt heater has been turned ON This allows the user to place the inner melt heater in the en trant well of the cell to initiate the inner melt Once the inner melt is initi ated the heater is removed from the cell The unit automatically de energizes the heater at the appropriate time After the outer melt of Hart Scientific Manual Rev 140901 17 6 Operation A Melting Curve of Gallium in Model 9230 Cell 43002 12 28 2000 1 8 2001 2 843070 2 843075 2 843080 2 843085 2 843090 2 843095 2 843100 0 20 40 60 80 100 120 140 160 180 200 Time hours Bridge Reading Rx Rs 0 5 mK Figure 4 Typical Melting Curve of Gallium the cell has been appropriately initiated the unit changes into the main tenance mode and the block temperature resets to 29 86 C After 30 to 60 minutes stabilization time the unit is ready for use The duration of the melt plateau varies depending on usage but lengths of five days or lon ger is achievable 6 3 Correction for Pressure Difference The melting p
14. oint of gallium as mentioned earlier is defined as the phase equilibrium between the liquid phase and solid phase of pure gal lium at a pressure of 101 325 Pa P0 The actual pressure P in a gallium cell may not be exactly the standard value During the course of manu facturing the fixed point cell it is easier to seal the cell if the pressure in the cell is a little lower than room pressure The actual pressure value in the cell just at the melting point is measured at Hart Scientific so that the correction for the difference of the pressure can be made later Table 2 of the ITS 90 gives the data of dT dP for all the defining fixed points For the melting point of gallium dT dP 2 0 x 10 8 C Pa Therefore the ac tual equilibrium temperature t can be calculated using the following equation Actual Equilibrium Temperature Equation t C x P P C Pa 29 7646 20 10 8 0 Furthermore during the measurement at the melting point the sensor of an SPRT is usually placed at an average height which is 0 143 m 0 168 m 0 025m lower than the surface of the gallium and where the pres sure is higher than that at the surface due to the static head The correc tion calculated according to the data given in Table 2 of the ITS 90 is 0 000172 C The equilibrium temperature at an immersion depth of 0 143 m can be calculated using the following equation Pr
15. ry convenient There is widespread application for the melting point of gallium in biologic environmental oceanographic geo logical and energy research Hart Scientific Manual Rev 140901 5 2 Introduction 6 Manual Rev 140901 5943 2 Introduction 3 Specifications and Environmental Conditions 3 1 Specifications Reproducibility 0 05 mK 0 00005 C Cell Uncertainty k 2 0 08 mK 0 15 mK 0 00008 C 0 000015 C Certification k 2 0 1 mK Purity of Gallium 99 99999 Cell Outer Diameter 38 1 mm Cell Overall Height 250 1 mm 0Entrant Well Inner Diameter 8 2 mm Immersion Depth 1 168 0 mm 1Depth is measured from the bottom of the entrant well to the upper surface of the gal lium 3 2 Environmental Conditions Although the instrument has been designed for optimum durability and trouble free operation it must be handled with care The instrument should not be operated in an excessively dusty or dirty environment The instrument operates safely under the following conditions temperature range 5 35 C 41 95 F ambient relative humidity 15 50 pressure 75kPa 106kPa mains voltage within 10 of nominal vibrations in the calibration environment should be minimized altitudes less than 2 000 meters 3 3 Warranty Hart Scientific Inc Hart warrants this product to be free from defects in material and workmanship under normal use and service for
16. tead of oil as the bath fluid and heat transfer medium Distilled water is cleaner and the viscosity of water is much lower than that of oil The water must be kept as clean as possible Long term direct contact between stainless steel and dirty water causes the cell case to rust The user should take the cell out of the bath and wipe the cell surface dry using clean tissue When the cell is not used for a period of time store the cell in the vertical position and in a clean place The surrounding temperature should be below 25 C Before freezing the cell remove all of the water from the entrant well using an in jector or other tool Never tilt the cell if you are not sure all of the gallium is frozen If the temperature of the cell goes below 0 C during freezing the water in the entrant well freezes and might break the entrant well The procedure for realization of a melting curve in a bath is as follows Make sure that all gallium is frozen before starting Maintain the bath at a temperature of 0 5 C below the melting point for at least 30 minutes Raise the temperature to 1 C above the melting point at a rate of 0 2 C per minute Maintain the bath at this temperature for 20 minutes Then in sert an 8 watt heater into the entrant well for 4 minutes After the 4 min utes decrease the bath to a temperature of 0 01 C to 0 1 C above the melting point Take the heater out of the entrant well and insert a pre heated thermometer into the
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