If MathJax does not have some symbols that old latex distribution (Tex filter) had you can use macros or unicode symbols.

For example you could try to add to MathJax configuration inside TeX: { ... } (after extensions)

TeX: {

extensions: ["mhchem.js"],

Macros: {

/* Wikipedia compatibility: these macros are used on Wikipedia */

empty: '\\emptyset',

P: '\\unicode{xb6}',

Alpha: '\\unicode{x391}', /* FIXME: These capital Greeks don't show up in bold in \boldsymbol ... */

Beta: '\\unicode{x392}',

Epsilon: '\\unicode{x395}',

Zeta: '\\unicode{x396}',

Eta: '\\unicode{x397}',

Iota: '\\unicode{x399}',

Kappa: '\\unicode{x39a}',

Mu: '\\unicode{x39c}',

Nu: '\\unicode{x39d}',

Pi: '\\unicode{x3a0}',

Rho: '\\unicode{x3a1}',

Sigma: '\\unicode{x3a3}',

Tau: '\\unicode{x3a4}',

Chi: '\\unicode{x3a7}',

C: '\\mathbb{C}', /* the complex numbers */

N: '\\mathbb{N}', /* the natural numbers */

Q: '\\mathbb{Q}', /* the rational numbers */

R: '\\mathbb{R}', /* the real numbers */

Z: '\\mathbb{Z}', /* the integer numbers */

/* some extre macros for ease of use; these are non-standard! */

F: '\\mathbb{F}', /* a finite field */

HH: '\\mathcal{H}', /* a Hilbert space */

bszero: '\\boldsymbol{0}', /* vector of zeros */

bsone: '\\boldsymbol{1}', /* vector of ones */

bst: '\\boldsymbol{t}', /* a vector 't' */

bsv: '\\boldsymbol{v}', /* a vector 'v' */

bsw: '\\boldsymbol{w}', /* a vector 'w' */

bsx: '\\boldsymbol{x}', /* a vector 'x' */

bsy: '\\boldsymbol{y}', /* a vector 'y' */

bsz: '\\boldsymbol{z}', /* a vector 'z' */

bsDelta: '\\boldsymbol{\\Delta}', /* a vector '\Delta' */

E: '\\mathrm{e}', /* the exponential */

rd: '\\,\\mathrm{d}', /* roman d for use in integrals: $\int f(x) \rd x$ */

rdelta: '\\,\\delta', /* delta operator for use in sums */

rD: '\\mathrm{D}', /* differential operator D */

/* example from MathJax on how to define macros with parameters: */

/* bold: ['{\\bf #1}', 1] */

RR: '\\mathbb{R}',

ZZ: '\\mathbb{Z}',

NN: '\\mathbb{N}',

QQ: '\\mathbb{Q}',

CC: '\\mathbb{C}',

FF: '\\mathbb{F}'

}

}

Just remember to use backslash when you type those new macros like \Z.

If you need some special character that does not have latex symbol you can use in mathjax \unicode{...} - for example \unicode{8484} creates \( \unicode{8484} \) - or you can even copy and paste (or write) normal unicode characters inside mathjax delimiters to mathematical notations (the number is useful only if you can't find or type an unicode character otherwise)