> For the complete documentation index, see [llms.txt](https://devdocs.olisystems.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://devdocs.olisystems.com/group1/api-functions/precipitation-point.md).

# Precipitation point flash

This function calculates the equilibrium solution at the precipitation point of a specified solid species by varying one inflow species.

## precipitation point

<mark style="color:green;">`POST`</mark> `https://api.olisystems.com/engine/flash/{dbs_file_id}/precipitation-point`

determine the minimum amount of an inflow species required to precipitate a solid

#### Headers

| Name          | Type   | Description            |
| ------------- | ------ | ---------------------- |
| Authorization | string | Bearer {access\_token} |
| Content-Type  | string | application/json       |

{% tabs %}
{% tab title="200 Please look at "API call blueprint" page on how to obtain results" %}

```
{
	"code": 200,
	"data": {
		"file_id": "dee854a6-59db-487d-ad08-a20dee691133",
		"jobId": "f6b3375e-cd0f-4ace-a5ee-71e047b76754",
		"resultsLink": "https://devapi.olisystems.com/result/flash/f6b3375e-cd0f-4ace-a5ee-71e047b76754?context=engine",
		"status": "IN PROGRESS"
	},
	"message": "Process execution started Successfully",
	"status": "SUCCESS"
}
```

{% endtab %}
{% endtabs %}

### Request payload

```javascript
{
    "params": {
        "temperature": {
            "value": 30.0,
            "unit": "°C"
        },
        "pressure": {
            "value": 1.5,
            "unit": "atm"
        },
        "solidToPrecipitate": "NACLPPT",
        "inflowToAdjust": "NACL",
        "inflows": {
            "unit": "mol",
            "values": {
                "H2O": 50.0,
                "CO2": 10.0,
                "NACL": 0.0,
                "BENZENE": 10.0
            }
        }
    }
}
```

| **params**         | type                                | description                                                                                |
| ------------------ | ----------------------------------- | ------------------------------------------------------------------------------------------ |
| temperature        | [valueObject](/terms-definition.md) | specified or initial guess temperature with unit                                           |
| pressure           | [valueObject](/terms-definition.md) | specified or initial guess pressure with unit                                              |
| solidToPrecipitate | string                              | specified **solid species** at precipitation point                                         |
| inflowToAdjust     | string                              | **inflow species** whose amount is to be adjusted to achieve precipitation point condition |

{% hint style="info" %}
**params.solidToPrecipitate** and **params.inflowToAdjust** are species and inflow names retrieved from the [chemistry information](/group1/api-functions/chemistry-info.md) call, under **result.species(trueName)** and **result.inflows(baseName)** respectively.&#x20;
{% endhint %}

{% hint style="info" %}
in addition to the inputs shown above some optional properties may also be specified. They can be viewed [here](/optional-inputs.md)
{% endhint %}

### Response (status = PROCESSED)

```javascript
{
    "code": 200,
    "data": {
        "result": {
           "calculatedVariables": [
                {
                    "name": "NACL",
                    "type": "inflow",
                    "unit": "mol",
                    "value": 5.531398835682553
                }
            ],
            ...<snip>...
        }
    }, 
    "message": "Results returned successfully", 
    "status": "PROCESSED"
}
```

The output of this calculation is the [stream output ](/stream-output-json.md)which is common result output for all OLI's flash calculations or an [error](/error-output.md). In addition to this output the result also contains the amount of the added  inflow (**params.inflowToAdjust**) can be conveniently retrieved from the **data.result.calculatedVariables** array

| <p>data.result.calculatedVariables</p><p><a href="/pages/-MKpla3yKkV7cet4Iee_"> </a><a href="/pages/-MKpla3yKkV7cet4Iee_">\[ { } ]</a></p> | type   | description                                                  |
| ------------------------------------------------------------------------------------------------------------------------------------------ | ------ | ------------------------------------------------------------ |
| type                                                                                                                                       | string | type of calculated variable, i.e. inflow amount for "inflow" |
| name                                                                                                                                       | string | name of adjusted inflow species                              |
| value                                                                                                                                      | number | the final amount of adjusted inflow                          |
| unit                                                                                                                                       | string | [unit](/input-unit-set.md) of inflow amount                  |

### Survey Calculation

Survey calculation is supported for the variables below. Please refer to [Survey calculation](/survey-calculation.md) for explained input schema.

| supported **params.surveyInputs\[{}].field** |
| -------------------------------------------- |
| "/params/temperature/value"                  |
| "/params/pressure/value"                     |