Re #50 minor comments

Author: abuts

source/tutorial/introduction.rst

@@ -92,7 +92,7 @@ In our example, the layers can be either deuterated or hydrogenated, and the bul
    Lipid Monolayer alongside with slab model parameters used in reflectivity calculations. Air/substrate case. 
 
 We are going to analyse our monolayer data using a standard `slab model <https://www.reflectometry.org/learn/3_reflectometry_slab_models/the_slab_model.html>`_.
-In this model, we approximate our experimental model as a series of layers with a known thickness, roughness and hydration which affects SLD.
+In this model, we approximate our experimental model as a series of layers with a known thickness, roughness, SLD and hydration which modifies SLD.
 The way that this is represented in the RAT model definition is by a list of **Parameter** objects which represent a given quantity (such as a thickness or hydration or SLD directly),
 and then a list of **Layer** objects which group together these parameters to describe each layer. (See :numref:`LipidMonolayerWithPar` above) Layers are then grouped together in a **Contrast** object which
 describes the slab model and matches it up to the experimental data to which the model will be compared. In this project we have two contrasts representing