# Isothermal flash

This method is the most common thermodynamic flash function and is used to determine the equilibrium solution output at a constant temperature and pressure.

## isothermal 

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

run an isothermal flash calculation

#### 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 to find out 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"
        },
        "inflows": {
            "unit": "mol",
            "values": {
                "H2O": 50.0,
                "CO2": 10.0,
                "NACL": 20.0,
                "BENZENE": 10.0
            }
        }
    }
}
```

| **params**  | type                                | description                                                                  |
| ----------- | ----------------------------------- | ---------------------------------------------------------------------------- |
| temperature | [valueObject](/terms-definition.md) | specified temperature with [unit](/input-unit-set.md)                        |
| pressure    | [valueObject](/terms-definition.md) | specified pressure with [unit](/input-unit-set.md)                           |
| inflows     | object                              | specified inflow species composition, see [Inflows Input](/inflows-input.md) |

{% 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 %}

{% hint style="info" %}
If kinetic reactions are defined in the chemistry model, kinetic calculation inputs are required to be specified. A detailed description can be found [here](/kinetic-calculation-inputs.md).
{% endhint %}

### Response (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).

### 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"                     |


---

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Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://devdocs.olisystems.com/group1/api-functions/isothermal.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.