# Freezing Point Depression Calculator API

> For the complete documentation index, see [llms.txt](/llms.txt).

Freezing point depression (delta-Tf = i * Kf * m) from molality or from solute/solvent mass, with a van't Hoff factor for ionic solutes.

Use this endpoint to add the tool to your app, site, workflow, or agent without rebuilding formulas, validation, examples, and docs.

- Slug: `freezing-point-depression-calculator`
- Category: `science`
- Version: `2026-04-22`
- Credits per successful call: 1
- Starts on: free
- Max payload: 65536 bytes
- Privacy mode: `hash_only`
- Available on: free, starter, pro, business, scale
- Browser tool: https://miniwebtool.com/freezing-point-depression-calculator/

## Endpoint

`POST https://api.miniwebtool.com/v1/tools/freezing-point-depression-calculator/run`

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `kf` | `float` | no | cryoscopic constant, degC*kg/mol |
| `pure_fp` | `float` | no | freezing point of the pure solvent, degC |
| `molality` | `float | None` | no | solute molality, mol/kg |
| `solute_mass` | `float | None` | no | grams of solute, used with molar_mass+solvent_mass instead of molality |
| `molar_mass` | `float | None` | no | solute molar mass, g/mol |
| `solvent_mass` | `float | None` | no | grams of solvent |
| `solute_type` | `str` | no | nonelectrolyte | binary | ternary | quaternary | quinary | custom Choices: nonelectrolyte, binary, ternary, quaternary, quinary, custom |
| `vant_hoff_factor` | `float | None` | no | override the van't Hoff factor i directly |

## Example request

```json
{
  "kf": 1.86,
  "pure_fp": 0,
  "molality": 0.5,
  "solute_type": "binary"
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/freezing-point-depression-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"kf":1.86,"pure_fp":0,"molality":0.5,"solute_type":"binary"}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "freezing-point-depression-calculator",
  "tool_version": "2026-04-22",
  "credits_used": 1,
  "result": {}
}
```

## Errors

Errors are RFC 7807 `application/problem+json`. Branch on `code`, not `title`.

## MCP

Agents can discover and call this tool through `https://api.miniwebtool.com/mcp` or `https://api.miniwebtool.com/v1/mcp` using MCP `tools/list` and `tools/call`.

## Frequently asked

### What does the Freezing Point Depression Calculator API do?

Freezing point depression (delta-Tf = i * Kf * m) from molality or from solute/solvent mass, with a van't Hoff factor for ionic solutes. Use it to add this utility without rebuilding formulas, validation, examples, and documentation.

### How much does one call cost?

1 credit per successful call. Failed calls do not bill.

### What parameters are required?

Required fields: (none). Full schema at `https://api.miniwebtool.com/v1/openapi.json`.

### Is this deterministic?

Yes. Same input, same output. Tool version: 2026-04-22.