Button: From Composition
Buffer Components Form
The purpose of the Buffer Components form is to allow the user to enter components of a buffer and then to have Sednterp interpolate a buffer density and/or viscosity for the buffer. Standard tables of single component buffer data have been fit by polynomials. Sednterp computes density increments for each component at the user entered concentration and adds these increments together to compute a final buffer density or viscosity. See the theory section for more complete information on the formulae involved.
On the upper right hand corner are two buttons and indicator lights that tell the user if the buffer components form is computing density or viscosity. Changing from Density to Viscosity (or vice-versa) will cause Sednterp to accept as final the density calculation presently shown on the screen and then to compute a viscosity based on the same buffer components. The list of available components is different for density and viscosity, so sometimes it is not possible for Sednterp to recreate the buffer components from one mode to the other. If this occurs, Sednterp will warn the user with a message box. If the user has data and a polynomial fitting program available, a new entry in the interpolating database can be entered from the Main form.
On the form are two list boxes. On the right is a list of all components for which table data has been fit. On the left is a list of all components in the present buffer. To add a component to the buffer, choose it in the left hand list box (double click, press the add button or press Return). The text box in the upper right hand corner will be enabled for the user to enter the concentration of this component. Type in the Molar concentration and then press the return key. The user must enter a concentration for each component.
To modify the concentration of a component already added to the buffer, choose the component in the right hand list and add it again as a new component; Sednterp will automatically remove the old entry. Or, double click on the components old concentration in the far right list box; Sednterp will immediately enable the concentration text box on the upper right hand corner. To remove a component, choose the component in the left hand list box (double click, press the remove button, or press return).
The maximum allowable concentration that can be entered for any component depends on the original table. If a concentration higher than the available interpolation maximum is entered, Sednterp will notify the user and ask for a new concentration. Typing in the search boxes at the bottom of each list box initiates a alphabetical search for whatever is typed in the search box. This enables the user to quickly find a component in a long list. The standard value of the density or viscosity interpolated for a buffer is shown on the top center text box. This value is at 20 degrees C. If the experiment is a different temperature than 20 or heavy water is present, the actual density used in further calculations is corrected for the experimental temperature. Temperature correction is also applied on the main form to viscosity calculations. This value is indicated in the lower right text box.
If the buffer has heavy water in it, the density calculation can add in the density of heavy water components. Pressing the Heavy button will bring up a small form where the percentages of deuterium and oxygen 18 can be entered. Buffer component lists can be saved to and read from special Sednterp text files by pressing the Read and Write buttons on the bottom of the form, although this is not necessary since the buffer composition data is also stored directly in the database. This capability is primarily provided for backward compatibility with pre-release versions of Sednterp.
Pressing OK returns to the Main form and enters the buffer components as listed. Pressing Cancel returns the Main form to its previous state.