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# Long description

Figure 14 On the left is the chemical formula 'Na H subscript 2 P O subscript 4'. Four arrows, each labelled with a temperature, point to the right.

The first arrow, which is labelled '250 degrees C', points to the formula 'Na subscript 2 H subscript 2 P subscript 2 O subscript 7'. To the right of this, in brackets, is a structure which starts with Na superscript + then superscript minus O, horizontal line P. Above the P a double vertical line goes to an O, while below the P a single vertical line goes down to an 'O H'. From the P, a horizontal line goes to an O, then on to another P. Once again, above the P a double vertical line goes to an O, while below the P a single vertical line goes down to an 'O H'. From the P, a horizontal line goes to an 'O superscript minus, then superscript + Na.

The second arrow, which is labelled 'greater than 250 degrees C', points to '( Na P O subscript 3 ) subscript n'. In brackets after this it says 'insoluble metaphosphate; n very large'.

The third arrow is labelled '630 degrees C' and points to '(Na P O subscript 3 ) subscript 3'. To the right of this is a structure: left square bracket, a structure containing 3 Ps and 9 Os, right square bracket, superscript '3 minus', 3 Na superscript +. The structure within the square brackets is a ring of three Ps, with an O between adjacent Ps. (The Os are all a little lower than the Ps.) Each P also has a double vertical line up to an O, and another O outside the ring, and once again a little lower than the P.

The final arrow is labelled '800 degrees C' and points to 'molten liquid (Na P O subscript 3 ) subscript n'.