diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4895abe06..2eb59a98d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## Features
 
+-   Store variable slices in model for inspection ([#925](https://github.com/pybamm-team/PyBaMM/pull/925))
+-   Made t_plus (optionally) a function of electrolyte concentration, and added (1 + dlnf/dlnc) to models ([#921](https://github.com/pybamm-team/PyBaMM/pull/921))
 -   Added `DummySolver` for empty models ([#915](https://github.com/pybamm-team/PyBaMM/pull/915))
 -   Added functionality to broadcast to edges ([#891](https://github.com/pybamm-team/PyBaMM/pull/891))
 -   Reformatted and cleaned up `QuickPlot` ([#886](https://github.com/pybamm-team/PyBaMM/pull/886))
diff --git a/pybamm/discretisations/discretisation.py b/pybamm/discretisations/discretisation.py
index 431c812e7..9a84cffd3 100644
--- a/pybamm/discretisations/discretisation.py
+++ b/pybamm/discretisations/discretisation.py
@@ -137,6 +137,8 @@ class Discretisation(object):
         # Set the y split for variables
         pybamm.logger.info("Set variable slices for {}".format(model.name))
         self.set_variable_slices(variables)
+        # Keep a record of y_slices in the model
+        model.y_slices = self.y_slices_explicit
 
         # now add extrapolated external variables to the boundary conditions
         # if required by the spatial method
@@ -214,6 +216,7 @@ class Discretisation(object):
         """
         # Set up y_slices
         y_slices = defaultdict(list)
+        y_slices_explicit = defaultdict(list)
         start = 0
         end = 0
         # Iterate through unpacked variables, adding appropriate slices to y_slices
@@ -233,14 +236,18 @@ class Discretisation(object):
                             submesh = domain_mesh[i]
                             end += submesh.npts_for_broadcast_to_nodes
                         y_slices[child.id].append(slice(start, end))
+                        y_slices_explicit[child].append(slice(start, end))
                         start = end
             else:
                 end += self._get_variable_size(variable)
                 y_slices[variable.id].append(slice(start, end))
+                y_slices_explicit[variable].append(slice(start, end))
                 start = end
 
         # Convert y_slices back to normal dictionary
         self.y_slices = dict(y_slices)
+        # Also keep a record of what the y_slices are, to be stored in the model
+        self.y_slices_explicit = dict(y_slices_explicit)
 
         # reset discretised_symbols
         self._discretised_symbols = {}

Store variable slices
Store variable slices in the model after discretising, for easy inspection
diff --git a/tests/unit/test_discretisations/test_discretisation.py b/tests/unit/test_discretisations/test_discretisation.py
index ce4cf0838..48a09b98a 100644
--- a/tests/unit/test_discretisations/test_discretisation.py
+++ b/tests/unit/test_discretisations/test_discretisation.py
@@ -132,6 +132,8 @@ class TestDiscretise(unittest.TestCase):
 
         self.assertEqual(disc.y_slices[a.id][0], slice(0, 10, None))
 
+        self.assertEqual(model.y_slices[a][0], slice(0, 10, None))
+
         b_test = np.ones((10, 1))
         np.testing.assert_array_equal(
             model.variables["b"].evaluate(inputs={"b": b_test}), b_test

pip install -e .[dev,docs]
parse_log_pytest
requirements.txt
pytest pytest-cov pytest-xdist pytest-mock pytest-asyncio pytest
apt-get update apt-get install -y gcc gfortran
3.7
requirements-docs.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
alabaster==0.7.13
anyio==3.7.1
anytree==2.12.1
argon2-cffi==23.1.0
argon2-cffi-bindings==21.2.0
attrs==24.2.0
autograd==1.6.2
Babel==2.14.0
backcall==0.2.0
beautifulsoup4==4.13.3
black==23.3.0
bleach==6.0.0
casadi==3.7.0
certifi @ file:///croot/certifi_1671487769961/work/certifi
cffi==1.15.1
charset-normalizer==3.4.1
click==8.1.8
comm==0.1.4
coverage==7.2.7
cycler==0.11.0
debugpy==1.7.0
decorator==5.1.1
defusedxml==0.7.1
docutils==0.17.1
entrypoints==0.4
exceptiongroup==1.2.2
execnet==2.0.2
fastjsonschema==2.21.1
flake8==5.0.4
fonttools==4.38.0
future==1.0.0
guzzle-sphinx-theme==0.7.11
idna==3.10
imagesize==1.4.1
importlib-metadata==4.2.0
importlib-resources==5.12.0
iniconfig==2.0.0
ipykernel==6.16.2
ipython==7.34.0
ipython-genutils==0.2.0
ipywidgets==8.1.5
jedi==0.19.2
Jinja2==3.1.6
json5==0.9.16
jsonschema==4.17.3
jupyter==1.1.1
jupyter-console==6.6.3
jupyter-server==1.24.0
jupyter_client==7.4.9
jupyter_core==4.12.0
jupyterlab==3.5.3
jupyterlab-pygments==0.2.2
jupyterlab_server==2.15.2
jupyterlab_widgets==3.0.13
kiwisolver==1.4.5
MarkupSafe==2.1.5
matplotlib==3.5.3
matplotlib-inline==0.1.6
mccabe==0.7.0
mistune==3.0.2
mypy-extensions==1.0.0
nbclassic==1.2.0
nbclient==0.7.4
nbconvert==7.6.0
nbformat==5.8.0
nest-asyncio==1.6.0
notebook==6.5.7
notebook_shim==0.2.4
numpy==1.21.6
packaging==24.0
pandas==1.3.5
pandocfilters==1.5.1
parso==0.8.4
pathspec==0.11.2
pexpect==4.9.0
pickleshare==0.7.5
Pillow==9.5.0
pkgutil_resolve_name==1.3.10
platformdirs==4.0.0
pluggy==1.2.0
prometheus-client==0.17.1
prompt_toolkit==3.0.48
psutil==7.0.0
ptyprocess==0.7.0
-e git+https://github.com/pybamm-team/PyBaMM.git@13a0ca0f666549f8561fd5a87a2487e628b4c3a2#egg=pybamm
pycodestyle==2.9.1
pycparser==2.21
pyflakes==2.5.0
Pygments==2.17.2
pyparsing==3.1.4
pyrsistent==0.19.3
pytest==7.4.4
pytest-asyncio==0.21.2
pytest-cov==4.1.0
pytest-mock==3.11.1
pytest-xdist==3.5.0
python-dateutil==2.9.0.post0
pytz==2025.2
pyzmq==26.2.1
requests==2.31.0
scikit-fem==8.1.0
scipy==1.7.3
Send2Trash==1.8.3
six==1.17.0
sniffio==1.3.1
snowballstemmer==2.2.0
soupsieve==2.4.1
Sphinx==4.3.2
sphinxcontrib-applehelp==1.0.2
sphinxcontrib-devhelp==1.0.2
sphinxcontrib-htmlhelp==2.0.0
sphinxcontrib-jsmath==1.0.1
sphinxcontrib-qthelp==1.0.3
sphinxcontrib-serializinghtml==1.1.5
terminado==0.17.1
tinycss2==1.2.1
tomli==2.0.1
tornado==6.2
traitlets==5.9.0
typed-ast==1.5.5
typing_extensions==4.7.1
urllib3==2.0.7
wcwidth==0.2.13
webencodings==0.5.1
websocket-client==1.6.1
widgetsnbextension==4.0.13
zipp==3.15.0

name: PyBaMM
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2022.12.7=py37h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.4.4=h6a678d5_1
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - pip=22.3.1=py37h06a4308_0
  - python=3.7.16=h7a1cb2a_0
  - readline=8.2=h5eee18b_0
  - setuptools=65.6.3=py37h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.38.4=py37h06a4308_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - alabaster==0.7.13
      - anyio==3.7.1
      - anytree==2.12.1
      - argon2-cffi==23.1.0
      - argon2-cffi-bindings==21.2.0
      - attrs==24.2.0
      - autograd==1.6.2
      - babel==2.14.0
      - backcall==0.2.0
      - beautifulsoup4==4.13.3
      - black==23.3.0
      - bleach==6.0.0
      - casadi==3.7.0
      - cffi==1.15.1
      - charset-normalizer==3.4.1
      - click==8.1.8
      - comm==0.1.4
      - coverage==7.2.7
      - cycler==0.11.0
      - debugpy==1.7.0
      - decorator==5.1.1
      - defusedxml==0.7.1
      - docutils==0.17.1
      - entrypoints==0.4
      - exceptiongroup==1.2.2
      - execnet==2.0.2
      - fastjsonschema==2.21.1
      - flake8==5.0.4
      - fonttools==4.38.0
      - future==1.0.0
      - guzzle-sphinx-theme==0.7.11
      - idna==3.10
      - imagesize==1.4.1
      - importlib-metadata==4.2.0
      - importlib-resources==5.12.0
      - iniconfig==2.0.0
      - ipykernel==6.16.2
      - ipython==7.34.0
      - ipython-genutils==0.2.0
      - ipywidgets==8.1.5
      - jedi==0.19.2
      - jinja2==3.1.6
      - json5==0.9.16
      - jsonschema==4.17.3
      - jupyter==1.1.1
      - jupyter-client==7.4.9
      - jupyter-console==6.6.3
      - jupyter-core==4.12.0
      - jupyter-server==1.24.0
      - jupyterlab==3.5.3
      - jupyterlab-pygments==0.2.2
      - jupyterlab-server==2.15.2
      - jupyterlab-widgets==3.0.13
      - kiwisolver==1.4.5
      - markupsafe==2.1.5
      - matplotlib==3.5.3
      - matplotlib-inline==0.1.6
      - mccabe==0.7.0
      - mistune==3.0.2
      - mypy-extensions==1.0.0
      - nbclassic==1.2.0
      - nbclient==0.7.4
      - nbconvert==7.6.0
      - nbformat==5.8.0
      - nest-asyncio==1.6.0
      - notebook==6.5.7
      - notebook-shim==0.2.4
      - numpy==1.21.6
      - packaging==24.0
      - pandas==1.3.5
      - pandocfilters==1.5.1
      - parso==0.8.4
      - pathspec==0.11.2
      - pexpect==4.9.0
      - pickleshare==0.7.5
      - pillow==9.5.0
      - pkgutil-resolve-name==1.3.10
      - platformdirs==4.0.0
      - pluggy==1.2.0
      - prometheus-client==0.17.1
      - prompt-toolkit==3.0.48
      - psutil==7.0.0
      - ptyprocess==0.7.0
      - pycodestyle==2.9.1
      - pycparser==2.21
      - pyflakes==2.5.0
      - pygments==2.17.2
      - pyparsing==3.1.4
      - pyrsistent==0.19.3
      - pytest==7.4.4
      - pytest-asyncio==0.21.2
      - pytest-cov==4.1.0
      - pytest-mock==3.11.1
      - pytest-xdist==3.5.0
      - python-dateutil==2.9.0.post0
      - pytz==2025.2
      - pyzmq==26.2.1
      - requests==2.31.0
      - scikit-fem==8.1.0
      - scipy==1.7.3
      - send2trash==1.8.3
      - six==1.17.0
      - sniffio==1.3.1
      - snowballstemmer==2.2.0
      - soupsieve==2.4.1
      - sphinx==4.3.2
      - sphinxcontrib-applehelp==1.0.2
      - sphinxcontrib-devhelp==1.0.2
      - sphinxcontrib-htmlhelp==2.0.0
      - sphinxcontrib-jsmath==1.0.1
      - sphinxcontrib-qthelp==1.0.3
      - sphinxcontrib-serializinghtml==1.1.5
      - terminado==0.17.1
      - tinycss2==1.2.1
      - tomli==2.0.1
      - tornado==6.2
      - traitlets==5.9.0
      - typed-ast==1.5.5
      - typing-extensions==4.7.1
      - urllib3==2.0.7
      - wcwidth==0.2.13
      - webencodings==0.5.1
      - websocket-client==1.6.1
      - widgetsnbextension==4.0.13
      - zipp==3.15.0
prefix: /opt/conda/envs/PyBaMM

tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_adding_1D_external_variable
tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_mass_matirx_inverse
tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_add_internal_boundary_conditions tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_adding_0D_external_variable tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_adding_0D_external_variable_fail tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_adding_2D_external_variable_fail tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_broadcast tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_broadcast_2D tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_check_tab_bcs_error tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_concatenate_in_order tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_concatenation tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_concatenation_2D tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_concatenation_external_variables tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_concatenation_of_scalars tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_discretise_slicing tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_discretise_spatial_operator tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_exceptions tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_no_mesh tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_complex_expression tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_dict tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_empty_model tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_model_concatenation tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_model_dae tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_model_fail tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_model_not_inplace tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_model_ode tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_symbol_base tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_variables_dict tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_process_with_no_check tests/unit/test_discretisations/test_discretisation.py::TestDiscretise::test_secondary_broadcast_2D
pybamm/discretisations/discretisation.py CHANGELOG.md
pybamm/discretisations/discretisation.py CHANGELOG.md