text: import streamlit as st
  
  
  def main():
      st.title("Welcome.")
  
      st.subheader("Get VLE data from [DDBST's](http://www.ddbst.com/en/EED/VLE/VLEindex.php) online database")
      st.write("The algorithm scours through all the vapor-liquid equilibrium data at DDBST and"
               " finds the complete VLE data of the chosen pair of compounds")
      # st.image('ddbst_site.png', width=750)
  
      st.subheader("Try different correlative models")
      st.write("Note: These models can only be used for binary isothermal vapor-liquid equilibrium data.")
      st.markdown(r'''|Model|$G^E$|$RTln\gamma_1$|$RTln\gamma_2$|
                      |:---:|:---:|:---:|:---:|
                      |Margules|$Ax_1x_2$|$Ax_2^2$|$Ax_1^2$|
                      |Redlich-Kister|$x_1x_2(A+B(x_1-x_2))$|$x_2^2(A-B+4Bx_1)$|$x_1^2(A+B-4Bx_2)$|
                      |van-Laar|$\frac{x_1x_2}{G^E}=\frac{x_1}{B} + \frac{x_2}{A}$|$\frac{A}{\big(1+\frac{Ax_1}{Bx_2}\big)^2}$|$\frac{B}{\big(1+\frac{Bx_2}{Ax_1}\big)^2}$| 
                      |Truncated Wohls expansion|$RT(2a_{12}z_1z_2(x_1q_1+x_2q_2))$ $z_i = \frac{x_iq_i}{\sum_j x_jq_j}$|$RT(2a_{12}q_1z_2^2)$|$RT(2a_{12}q_2z_1^2)$|''')
  
      st.subheader("UNIQUAC Model for isobaric data")
      st.write(r"$G^E = (G^E)^C + (G^E)^R$ = Combinatorial + Residual")
      st.write(r"The combinatorial part quantifies the effect of structure of molecule "
               r"while the residual part describes the interactions between the molecules.")
      st.write(r"$\gamma_i^C = \frac{\phi_i}{x_i} + \frac{z}{2} q_i \ln\big( \frac{\theta_i}{\phi_i} \big) + l_i - \frac{\phi_i}{x_i}\sum_j(x_j l_j)$")
      st.write(r"$\gamma_i^R = q_i \bigg(1 - \ln \big( \sum_j(\theta_j \tau_{ji}) \big) - \sum_j \big( \frac{\theta_j \tau_{ij}}{\sum_k{(\theta_k \tau_{kj})}} \big) \bigg)$")
      st.write("where")
      st.write(r"$\phi_i = \frac{x_i r_i}{\sum_j x_j r_j}$")
      st.write(r"$\theta_i = \frac{x_i q_i}{\sum_j x_j q_j}$")
      st.write(r"$l_i = \frac{z}{2}(r_i - q_i) - (r_i - 1)$")
      st.write(r"$\ln( \tau_{ij} ) = -\big( \frac{u_{ij} - u_{jj}}{RT} \big)$")
      st.write(r"$\gamma_i = \gamma_i^C \times \gamma_i^R$")
  
      st.subheader("Get McCabe-Thiele Plots instantly")
      st.write(
          "The McCabe-Thiele method is used to determine the number of equilibrium stages for a distillation column. "
          "The vapor-liquid equilibrium data is a crucial part of analysis and design of a distillation column.")
      st.write(
          r''' This tool gives the flow rates of distillate and bottoms streams, minimum reflux ratio and it has an option for total reflux conditions too.''')
  
      # st.subheader("Updates")
      # st.text("23/3/21: Added UNIQUAC model")
      # st.text("29/7/20: Added Truncated Wohls model, enabled viewing of isobaric datasets.")
      # st.text("25/7/20: Added correlative models.")
  